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PRACTICAL 
CEMENT TESTING 



W, PURVES TAYLOR, M.S., C.E. 

Engineer in Charge Philadelphia Munieiptti 
Te^^ting Laboratories 



Nkw York 

\ni<()N C. (■ LA Iv «N 

13 2 1 Park Kow 






LIBRARY of CONGRESS 
Two Coirtcs Roccivwl 

JAN 6 i906 

Copyrlfftit Entry 

CLASS CC XXc. Ho. 

COPY B. 



PREFACE. 

Although during the past year or two, the additions to the 
literature on cement and concrete have been especially notable, 
it nevertheless has appeared to the author that a complete de- 
scription of the methods of handling practical tests of cement 
has not yet been brought before the public. The methods usu- 
ally given in text books assume too much knowledge for the use 
of the student or beginner, while to the practical operator the 
directions are too general to be of much value. The excellent 
standard methods of testing recently issued by committees of 
several technical societies have already done much to promote 
uniformity in testing, but are of little real assistance either to 
the novice or the expert in enabling him to increase the ac- 
curacy or to simplify the routine of his work. This volume 
therefore has been designed primarily for the use of the stu- 
dent, the novice, and the practical operator in conducting actual 
routine tests of cement to determine its suitability for purposes 
of construction, but it is hoped that both the expert and the 
engineer who directs this work may also find something of in- 
terest in its pages. 

The general scope of the book covers a description of the 
properties of cement, the objects of the various tests, the 
methods of conducting them, the common influences and errors 
that are most likely to affect the determinations, and the prac- 
tical interpretation of the results which are finally obtained. 
No attempt has been made to consider the practical use of ce- 
ment and concrete except in so far as the conditions of actual 
work regulate the use of the various tests, while the data given 
are also applicable more to the conduct of tests than to the 
final use of the material. In other words, the scope of the book 
is intended to cover only the methods and the application of 
the tests of cement commonly employed in routine work, and 
not to consider theoretical properties, investigations of a re- 
search character, nor the use of cement. 

Chapters I., II. and III. are of an introductory nature, and 
are included only for the information of the student, anil for the 



jy PREFACE. 

logical development of the subject. The constitution of cement 
is considered very briefly, while the chapter on manufacture is 
purely descriptive and makes no attempt at being technical. 

The body of the book, Chapters IV. to XII., is devoted to the 
conduct of routine tests of cement. The chapter on Chemical 
Analysis was prepared in collaboration with Mr. Charles S. 
Reeve, Chemist of the Philadelphia Laboratories. 

Chapter XIII. deals with simple tests by which the character 
of a cement may be ascertained with practically no apparatus, 
and which might be of considerable service to the small con- 
sumer or to the expert when it is impracticable to obtain ap- 
paratus to make tests in the orthodox manner. 

The practical operation of a cement laboratory is considered 
in Chapter XIV., which also describes the organization, the 
labor required, and the cost of testing. 

To avoid an endless number of qualified statements, in de- 
scribing the different properties and tests, the body of the book 
is devoted entirely to Portland cement, while in Chapter XV. 
is given a description of the properties and tests of natural, 
improved, slag, sand, and other varieties of cement. 

Chapter XV^I. is devoted to the subject of cement specifica- 
tions, while the different Appendices give the standard speci- 
fications and methods of testing issued by various scientific 
bodies. 

The methods of testing used in the author's laboratory are 
given at some length throughout the course of the book, and it 
is hoped that the frequent allusions to them will be pardoned on 
account of the long and varied experience of the laboratory, 
and on account of the large amount of testing performed, which 
has required both development of system and simplification of 
method. 

The author wishes to express his appreciation of the kindness 
of Mr. George S. Webster, Chief Engineer of the City of Phila- 
delphia, in permitting him to describe the methods employed, 
and to use data obtained in the Philadelphia Laboratories, and 
also to acknowledge the interest that has enabled the Labora- 
tories to attain their present stage of development. 

Acknowledgements for the use of cuts are also due to The 
Allis-Chalmers Co., J. W. Bramwell, The Bonnot Co., The Brad- 



PREFACE. V 

ley Pulverizer Co., The Cement Age, F. L. Smidth & Co., The 
Geo. V. Cresson Co., F. D. Cummer & Son Co., The Fairbanks 
Co., The Kent Mill Co., Lathbury & Spackman, Tinius Olsen & 
Co., Thos. Prosser & Son, Riehle Bros. Testing Machine Co., 
Frederick W. Taylor, Henry Troemner and the International 
Instrument Co. 

W. PURVES TAYLOR. 
January i, 1906. 



TABLE OF CONTENTS 

Page 
CHAPTER I.— CLASSIFICATION AND STATISTICS 1 

Definitions. — Classification. — Distinguishing character- 
istics of the different varieties. — Historical data. — Statistics 
of the Portland cement industry. 



CHAPTER II.— COMPOSITION AND CONSTITUTION 7 

The components of Portland cement. — Silica. — Lime. — 
Alumina. — Iron oxide. — Magnesia. — Sulphuric acid. — Sul- 
phur. — Alkalies. — Carbonic acid. — The constitution of Port- 
land cement. — Various theories. 

CHAPTER III.— MANUFACTURE 15 

Raw materials. — Calculation of mixtures. — Processes of 
manufacture. — Dry process with rotary kilns. — Dry process 
with stationary kilns. — Wet process with rotary kilns. — Wet 
process with stationary kilns. — Portland cement from slag. 
— Essentials to good manufacture. 

CHAPTER IV.— INSPECTION AND SAMPLING 34 

Reception and storage of shipments. — Shipments in bags 
and barrels. — Time to hold shipments for test. — Field in- 
spection. — Color of cement. — Weight of packages. — Methods 
of sampling. — Treatment of samples. 

CHAPTER v.— THE TESTING OF CEMENT 41 

Classification of tests. — Qualities necessary for a good 
cement to possess. — The common tests of cement. — The de- 
velopment of testing.— Methods of testing'. — Uniformity in 
testing. — Requisites for good testing. 

CHAPTER VI.— SPECIFIC GRAVITY 4G 

Definition, — Objects of test. — Underburning. — Adultera- 
tion. — Effect of seasoning. — Effect of composition. — Effect 
of fineness. — Effect of humidity. — The test of apparent den- 
sity. — Forms of apparatus. — Methods of operation. — Pre- 
liminary treatment of sample. — Sources of error. — Inter- 
pretation of results. 

CHAPTER VII.— FINENESS C3 

Necessity for fine grinding.— Objects of test. — Various 
methods of determining fineness. — Sieves. — Wire cloth. - 
Specifications for wire cloth. — Mechanical sifting. — Size and 
shape of sieves. — Treatment and size of sample. — Accuracy 
of test. — Methods of operation. — Sources of error. — Inter- 
pretation of results. 



viij CONTENTS. 

Page 

CHAPTER VIII.— TIME OF SETTING 80 

Definitions. — Objects of test. — Theory of setting. — Effect 
of composition. — Effect of seasoning. — Effect of mixing 
water.— Effect of fineness. — Effect of environment. — Rise 
of temperature during setting. — Normal consistency. — 
— Methods of determining consistency. — Forms of appa- 
ratus. — Methods of operation. — Sources of error. — Accuracy 
of test. — Interpretation of results. 

CHAPTER IX.— TENSILE STRENGTH 101 

Definition. — Objects of test. — Reasons for use of tensile 
test. — Neat versus sand tests. — Effect of composition. — 
Effect of seasoning. — Effect of fineness. — Effect of environ- 
ment. — Making briquettes. — Amount of mixing water. — 
Temperature of mixing water. — ^Purity of mixing water. — 
Sand. — Form of briquette. — Moulds. — Method of mixing and 
moulding. — Hand methods. — Mechanical methods. — Storage 
of briquettes.— Environment during setting. — Appliances for 
storing. — Marking briquettes. — Various types of testing 
machines. — Adaptability of the different types. — Form of 
clip. — Rate of stress. — Wet briquettes.— Number of speci- 
mens to test. — Accuracy of test. — The strength of Port- 
land cement. — Interpretation of results. 

CHAPTER X.— SOUNDNESS 156 

Definition. — Causes of unsoundness. — Effect of seasoning. 
— Effect of fineness. — Methods of determining soundness. — 
Measurements of expansion. — Normal lests. — Accelerated 
tests. — Methods of conducting accelerated tests. — Forms of 
apparatus. — Value of accelerated tests.— Interpretation of 
results. 

CHAPTER XI.— CHEMICAL ANALYSIS 184 

The components of cement. — Significance of analyses. — 
Methods of analysis. — General method. — Alternative and 
additional methods. — Rapid methods for control work. — The 
detection of adulteration. — Microscopical tests. — Equip- 
ment for chemical testing. — Value as a routine test. 

CHAPTER XII.— SPECIAL TESTS 212 

Compression tests. — Transverse tests. — Tests of adhesion. 
—Shearing tests. — Abrasion tests. — Porosity. — Permea- 
bility. — Yield tests of mortar. — Tests of sand. — Tests of 
stone. 

CHAPTER XIII.— APPROXIMATE TESTS 226 

The use of approximate tests. — Tests of fineness. — Tests 
of setting. — Tests of strength, by the tensile test. — Tests of 
strength by the transverse test. — Tests of soundness. — 
Tests of purity. — Apparatus. — Interpretation of results. 

CHAPTER XIV.— PRACTICAL OPERATION 239 

Equipment of a laboratory. — Amount of labor required. — 
Cost of operation. — Organization of the laboratory. — Re- 
cording systems. 



CONTENTS. ix 

Page 
CHAPTER XV.— OTHER VARIETIES OF CEMENT 252 

Natural cements, their manufacture, properties, tests 
and the interpretation of results. — Improved cements. — 
Pozzuolana cements. — Slag cements. — Sand cements. — 
Mixed cements. 

CHAPTER XVI.— SPECIFICATIONS 275 

Discussion of specifications. — Standard specifications. — A 
form of specification for Portland and natural cements. — 
The general interpretation of specifications. 

APPENDIX A. — Standard methods of testing, proposed by the Com- 
mittee of the American Society of Civil Engineers 287 

APPENDIX B.— Standard method for the chemical analysis of 
cement, proposed by the Committee of the New York Section 
of the Society for Chemical Industry 296 

APPENDIX C. — Standard specifications for Portland and natural 
cement, adopted by the American Society for Testing 
Materials 299 

APPENDIX D. — Specifications for Portland, natural and puzzolan 

cement, adopted by the Corps of Engineers, U. S. Army.... 303 

APPENDIX E. — British standard specifications for Portland cement, 

issued by the Engineering Standards Committee 308 

APPENDIX F. — Specifications for Portland cement, adopted pro- 
visionally by the Canadian Society of Civil Engineers 312 

APPENDIX G. — A list of reference books on cement and concrete. . 313 

INDEX 31G 



PRACTICAL CEMENT TESTING 



CHAPTER I. 

CLASSIFICATION AND STATISTICS. 

Definitions. — Hydraulic cement may be somewhat broadly de- 
fined as a material which, when pulverized and mixed with water 
into a paste, acquires the property of setting and hardening un- 
der water. In engineering construction, four classes of cement 
are generally recognized — (i) Portland cement, (2) natural 
cement, (3) Pozzuolana cement, (4) mixed or blended cement. 

Portland cement is the product resulting from the process of 
grinding an intimate mixture of calcareous and argillaceous 
materials, calcining the mixture to incipient fusion, and grind- 
ing the resulting clinker to a fine powder. It must contain no 
materials added subsequent to calcination other than small 
amounts of certain substances used to regulate its setting prop- 
erties. The German Association of Portland Cement ^lanu- 
facturers has adopted the following definition of Portland 
cement : 

"A hydraulic cementing material having a specific gravity of 
not less than 3.10 in the calcined condition, and containing not 
less than 1.7 parts bv weight of lime to one part each of silica, 
alumina, and ferric oxide, the material being prci)are{l by in- 
timately grinding the ravv' ingredients, calcining them to not less 
than clinkering temperature, and then reducing this clinker to a 
proper fineness." 

English and American societies* also have adopted standard 
definitions of Portland cement similar in tenor, although not as 
explicit, except that they limit the amount of substances that 
may be added after calcination to two or three i)er cent. 

Natural cement is the product resulting from the burning and 
subsequent pulverization of an argillaceous limestone or other 
suitable rock in its natural condition, the heat of burning being 
insufificient to cause vitrification. 



♦See Appendices. 



2 PRACTICAL CEMENT TESTING. 

This class of cement is also commonly known as ''Rosendale, ' 
it being; so named from the district in the eastern part of New 
York State which is the greatest producer of natural cement. 
This term, however, when applied to all naturals is a misnomer. 
In England the name "Roman" is applied to certain grades of 
this material. 

Pozzuolana cement is obtained by grinding together an inti- 
mate mixture of slaked lime and blast-furnace slag or volcanic 
scoria. The cement is not burned, the hydraulic ingredients 
being present only as a mechanical mixture. This material 
must not be confused with slag Portland, which is a regular 
Portland cement in v/hich the slag furnishes the silicious ingre- 
dients, thus replacing the clay or shale in the mix. 

Mixed cements cover a large variety of products made by 
combining the other forms of cement or by mixing them with 
an inert material. The so-called "second-grade" Portlands gen- 
erally belong in this class, since they consist usually of Portland 
cement mixed either with natural cement or with raw rock, 
cinder or slag. Sometimes, however, these cements are merely 
made of inferior clinker, in which case the>- are to be classed 
with Portlands. 'Improved cements" are naturals containing 
from 10 to 30 per cent, of Portland clinker. Sand cements are 
made by finely grinding a mixture of Portland cement and 
sand, usually in equal proportions. These varieties of mixed 
cements are those most commonly encountered, although many 
other forms are to be found on the market. 

Distinguishing Characteristics. — The distinguishing character- 
istics of Portland cement are — in manufacture, the use of an 
artificial mixture, the grinding before burning, and the calcina- 
tion to incipient fusion — and in use, its heavier weight, its slower 
set, and its greater strength. 

Natural cement is distinguished in manufacture by its produc- 
tion from a single variety of material, unground, and burned at 
a low heat, and in use by its lighter weight, quicker set, and 
lower strength in the earher stages of hardening. 

In what follows in this book, the discussion will be limited to 
Portland cement (except for Chapter XV.) , so that whenever the 
unqualified term cement is employed^ Portland cement alone is to 
be understood. 



CLASSIFICATION AND STATISTICS. 3 

Historical.* — Although Smeaton, when building the Ecldystone 
lighthouse in 1756, discovered that the addition of clay to lime 
would render it capable of setting under water, no real Portland 
cement was produced until 1824, when Joseph Aspdin, a brick- 
layer, of Leeds, England, took out a patent for producing a 
cement by calcining a mixture of lime and clay. He gave to it 
the name ''Portland" on account of its resemblance when hard- 
ened to the famous oolitic limestone, used extensively for build- 
ing, found in the ''Isle of Portland," a peninsula on the southern 
coast of England. The first works for producing this material 
were estabhshed at Wakefield by Aspdin in 1825, while the con- 
struction of the Thames tunnel in 1828 was the first important 
piece of engineering work to use it in any quantity. 

This early cement, however, was very different from that of 
modern days, chiefly in that the burning was never carried up 
to the point of vitrification, so that the elements could never 
have been properly combined. It was not until about 1845 
that the manufacture began to be placed upon a scientific basis, 
and Portland cement, as we now^ know it, to be produced. In 
Germany, the first works were established near Stettin in 1852, 
while 1875 niarked the beginning of the industry in the United 
States. 

Statistics of Industry. — The development of the Portland 
cement industry, particularly in the past decade, has been of such 
remarkable proportions, that a brief summary of statistics re- 
garding it cannot fail to show the importance of the scientific 
study of a material so widely employed. The following data 
are taken largely from the report of the Geological Survcyf for 
1903: 

Table I. shows the domestic production of Portland, natural 
and slag cements. It will be observed that the production of 
natural cement has remained practically constant for the past 
fifteen years, while the Portland production, particularly since 
1895, is remarkable in its rapid increase. The chief reason 
that Portland cement production, prior to 1895, advanced so 
slowly, was the deep-seated prejudice of our engineers against 

♦For more complete data on the history of cement consult Redprrar*'!. -mV- 
careous CTements," and f!ummings' "Anicrlcnn Cenicnts •' 

f'The production of Comont in lOm.' h- 1.. L. Kimhnll-ex nuM from Min- 
eral Resources of the United States" for lOO^-issued by Division of Mtnlng and 
Mineral Recources, U. S. Greoloplcal Survey. 



4 PRACTICAL CEMfiXT TESTING. 

the (loniostic and in favor of the forcii^n material. Even as late 
as the oml of the past decade, it was not uncommon for the 
specifications of imi)ortant work to call for foreign cement, or at 
•least for a cement "that shall be equal to the best German 
brands." The excellence of the domestic product and its 

TABLE I.— Total Production of Natural, Portland and Slag Cement in the 

United States. 1818-1903. 

(From Mineral Resources of the United States, 1903.) 

Year. 

1S18 to 1S30 

1S30 to 1840 

1840 to 1850 

1850 to i860 

i860 to 1870 

1870 to 1880 

1880 

I88I 

1882 

i^S3 

1884 

1S85 

1S86 

1S87 

1888 

l88q 

i8qo 

i8qi 

i8q2 

1803 

i8q4 

1805 

i8q6 

1807 

1808 

iSqg 

I QOO 

lOOI. 

IC)02 

iqo3 







Pozzuulana 


Natural. 


Portland. 


or Slag. 


300,000 






1,000.000 






4,250,000 







11,000,000 






16,420,000 






22,000,000 


82,000 





2.030,000 


42,000 




2,440,000 


60,000 




3,165,000 


85,000 


, 


4,190,000 


90,000 




4,000,000 


100,000 




4,100,000 


150,000 




4,186,152 


150,000 




6,692,744 


250,000 




6,253,295 


250,000 





6,531,876 


300,000 




7,082,204 


335'000 




7.451^535 


454.813 




8,211,181 


547.440 





7,411,815 


590,652 




7,563.488 


7q8,757 




7,741.077 


990.324 




7,970,450 


1.543.023 


12,265 


8,311,688 


2.677,775 


48,329 


8,418,924 


3,692,284 


150,895 


9,868,179 


5,652,266 


335,000 


8.383.519 


8,482,020 


446,609 


7.084,823 


12.711,225 


272,689 


8,044.305 


17,230,644 


478,555 


7.030,271 


22,342,973 


525,896 


209,132,526 


79,608,196 


2,270,238 



equality to the best foreign material is now, however, generally 
conceded. 

Table II. gives the distribution of production by States, Penn- 
sylvania leading both in the number of mills and in quantity of 
output. 

The distribution by sections (Table III.) divides the produc- 
tion into the "Lehigh district" of Pennsvlvania and Ne\v Jersey, 
the New York district, both of which operate on limestone, and 



CLASSIFICATION AND STATISTICS. 



TABLE II. — Production of Portland Cement in the United States in 1903, 

by States. 
(From Mineral Resources of the United States, 1903.) 



State. 

Alabama 

Arkansas 

California 

Colorado 

Georgia 

Illinois 

Indiana 

Kansas 

'Michigan 

Missouri 

New Jersey 

New York 

Ohio 

Pennsylvania . . . 
South Dakota. . . 

Texas 

Utah 

Virginia 

West Virginia. . . 



Tumber of 
Work.s. 


Quantity 
Barrels. 


3 

a I 

2 


631,151 
258,773 


5 
3 

d I 


1,257,500 

1,077.137 
1,019,682 


13 

r 2 

3 
12 

8 

n 

I 


1,955.183 
825,257 

2,693,381 

1,602,946 
729 519 

9.754.313 


2 





Value. 



$1,019,352 
436,535 



1,914.500 

1.347.797 
1,285,310 
2,674,780 
I 164,834 
2,944,604 
2,031,310 
998, 300 
11,205 892 



538,13^ 



690,105 



Total 78 22,342,973 $27,713,319 

(a) Includes product of Utah and South Dakota. 

(b) Includes product of Texas, 
(r) Includes product of Arkansas. 

{d) Includes product of Alabama, Georgia and West Virginia. 



TABLE III. — Showing the Development of the Portland Cement Industry in 

the United States. 
(From Mineral Resources of the United States, 1903.) 



Section. 

New York 

Lehigh and Northamp- 
ton counties, Pa., and 
Warren County, N. J. 

Ohio 

Michigan 

All other sections 

Total 

New York 

Lehigh and Northaiiip- 
ton counties, Pa., and 
Warren County, N. J. 

Ohio 

Michigan 

All other sections 

Total (>s 



Nurnbor 
of works. 

4 


QiMutity. 
Barrels. 

65,000 


Per 
cent. 

194 


Number 
of works. 

8 


Quantity. 
Harrols. 

465,832 


Per 
cent. 

5.5 


5 
2 

5 


201,000 
22,CXjO 

47 5"" 


60.0 
6.5 

14.1 

100.0 


15 

6 
6 
>5 

50 


6, 153,620 
5.U 215 
004,751^ 
003,504 

8,482,020 


72.6 

•6.3 

78 

7.8 


16 


335.500 


lOO.O 




1902. 

I, i5(),8()7 


0.8 








10 


'' 


l,tK)2,040 


72 


17 

7 

10 

21 


I(>,.SJ(),()2-.' 

5'>3.H3 
I 577.cx)0 
3,103.796 


<>2 s 
O.I 

180 


8 

>3 

29 


7-:«).5i<) 
1.955. »83 
5.730.403 


M 

«.7 

as.6 



17,230,04.1 



UXJ.O 



PRACTICAL CEMF.XT TESTING. 



the Ohio-Michigan district, which generally employs marl. The 
Lehigh district produces over half the Portland cement made 
in the country. The recent development of the industry in 
Michigan is also a feature of the table. 
The diagram, Fig. i, shows a comparison of the consumption 

Barrels 
32,000,000 

30,000,000 

28,000,000 

26,000,000 

24,000,000 

22,000.000 

20,000,000 

18,000,000 

16,000,000 



12,000,000 
10,000,000 
8,000,000 
6,000,000 
4,000,000 
2,000,000 



coaoootccDcoaocncr)iT)OD(ricPcr)(Tic;jcnoooo 

CDc0Q0C0a0C0COGDQ000CDaD00C0COaQcDGnCX>OlO> 

Years, 
YiG. I. — Diagram Showing the Quantity of Cement Consumed 
in the United States During the Twenty Years, 1883-1903. 

of Portland cement in the United States with the entire amount 
of hydraulic cement imported in the last few years, which illus- 
trates not only the growth of the industry, but also the marked 
increase in the ratio of domestic production to total consump- 
tion. 

















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==^^ — — ^^n 1 ; ^ ' i 







CHAPTER II. 

COMPOSITION AND CONSTITUTION. 

Composition. — The essential components of Portland cement 
are silica, alumina and lime. Other ingredients always occurring 
in appreciable quantities are iron, magnesia, alkalies, sulphuric 
and carbonic acids, and water. 

Le Chatelier has stated* the following to be the limits of these 
ingredients in good commercial cements : 

Silica 21 to 24 per cent. 

Alumina 6 " 8 

Iron oxide 2 " 4 

Lime 60 '' 65 '' 

Magnesia 0.5 '' 2 

Sulphuric acid 0.5 '* 1.5 

Carbonic acid and water . . . i *' 3 

Bleininger, in a chaptert on the Nature of Portland Cement, 
sets the following limits : 

Silica 19 to 26 per cent. 

Alumina 4 " 11 

Iron oxide 2 '' 5 

Lime 58 " 67 '' 

Magnesia o " 5 

Sulphuric acid o " 2.5 

Alkalies o " 3 

The percentages given b\ Le Chatelier should be considered 
as average rather than limiting values, since many good cements 
have an average composition largely out of these limits ; Hlein- 
inger's limits, on the other hand, are somewhat extreme. 

Table IV. gives the results of chemical analyses of many 
standard brands and serves to show the composition of conuner- 
cial cements. In addition to these important ingredients, the 
following usually occur in very small (juantities: Titanium, 
phosphoric acid, sulphur, manganese, silicious sand, coal ami 
ash from the kilns, flint and iron from the mills, etc. Tlie sum 
total of these elements, however, rarely e(|uals (Mie per cent. 

♦Tranwartions American Institute of Mining FinRlnocrs. IS'K^. , , . 

f'Manufac-ture cf Portland Comonts." by A. V. HleJniMKor. l-ourlh s.<rl.>s. 
Rullolin :{, Ohio Slato C.ooloKical Survey. 



PRACTICAL CEMEXT TESTIXC. 



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COMPOSITION AND CONSTITUTION. g 

Silica (SiOg). — Silica constitutes from 19 to 24 per cent, of a 
Portland cement, and combined with lime to form calcium sili- 
cate furnishes the active factor in its hardening. It should 
exist entirely in a combined state and not as quartz sand, in 
which condition it does not combine with the lime, and is inert 
in the subsequent reactions. 

Lime (CaO). — A well proportioned cement will contain from 59 
to 67 per cent, of lime, depending upon the amounts of silica 
and alumina present. Provided all of it exists in a combined 
state, the greater its amount, the higher will be the strength 
of the product. If, however, more lime is present than will 
combine with the silica and alumina, an unsound cement will 
result, since the excess of lime in slaking will expand and so 
cause disintegration. The recent demand for high strength 
values at early periods has caused many manufacturers to pro- 
duce very high limed cements, often passing the limit of safety 
unless exceptional care has been taken to so finel} grind the 
raw materials and to burn so perfectly that the theoretical limit 
of combination can be approximated. A high proportion of 
lime also requires greater heat in burning, and forms a slow- 
setting cement. 

*"Too low a proportion of lime, on the other hand, produces 
a fusible clinker, liable to overburning. This is especially the 
case with aluminous materials. If hard-burned, such mixtures 
give a fused clinker liable to fall to dust on cooling, hard to 
grind, and yielding slow-setting cement of poor hardening prop- 
erties. If light burned, an over-clayed mixture yields soft 
brownish clinker, grinding to a brownish, quick-setting cement 
of inferior strength." 

Alumina (ALO.j). — From 5 to 10 per cent, of alumina i> usually 
present in Portland cement, mostly combined as calcium alumin- 
ates, and since the setting ])roperties are due to these alumin- 
ates, the greater the proportion of this ingredient, the (|uicker 
will be the setting of the product. The ultimate tensile strength 
of high alumina cements is also apt to be inferior. The presence 
of alumina tends to facilitate the burning, since its compounds 
are much more fusible than those of silica, and it present in 



*S. B. Newberry in "Coiicreto. I'lain ;iml Itfiiifoicod." by F. W. Tiiyli^r ami 
6. E. Thompson. 



10 PRACTICAL CEMENT TESTING. 

excess make a mixture difficult to burn uniformly and hard to 
grind. 

Iron Oxide (FCoOg). — According to Le Chatelier, ferric oxide 
and calcium carbonate on burning yield products which slake 
with water and possess no hydraulic properties. Schott and 
Richardson, however, have prepared cements in which all of the 
alumina was replaced by iron, and therefore conclude that the 
function of these two ingredients is practically similar. The 
investigations of S. B. and W. B. Newberry also appear to show 
that the action of ferric oxide and alumina in promoting the 
combination of silica and lime is practically identical. The 
amount of iron usually present in Portland cements is less than 
4 per cent.; and it exerts but little influence on the physical prop- 
erties of the material. The dark gray color of cement is due 
to the presence of iron compounds, cement prepared from silica, 
alumina and lime only being colorless. 

Magnesia (MgO). — The role of magnesia in Portland cement 
has not yet been definitely determined. Certain investigators, 
including Le Chatelier, claim that magnesia may replace lime, 
and form silicates and aluminates of magnesia whose character- 
istics are similar to those of calcium. Others, including Erd- 
menger, Richardson and Newberry, consider that magnesia re- 
mains free in cement and is present only as an adulterant. 

Investigation of two or three failures of important engineer- 
ing works placed in sea water developed the fact that the con- 
crete was high in magnesia, but it has been claimed that its 
presence was due to a deposition of magnesian salts from the 
water, and that the magnesia originally present in the cement 
was not responsible for the failures. A committee of the Asso- 
ciation of German Portland Cement Manufacturers in 1895 
presented a report stating that their investigations had shown 
that a content of magnesia up to 8 per cent, was harmless. 
Dyckerhofif, however, presented a minority report, stating that 
his experiments had shown that more than 4 per cent, of mag- 
nesia, whether added to a normal mixture or substituted for an 
equivalent portion of lime, caused a steady falling off in the 
strength of the cement, although actual cracking was observed 
only with 8 or more per cent. S. B. Newberry has stated that 
he has made a cement containing 9 per cent, magnesia which 



COMPOSITION AND CONSTITUTION. u 

stood the boiling test, but that one containing 15 per cent, failed 
after several hours' boiling. 

American Portland cements contain on an average from 2 to 
4 per cent, magnesia, the latter value being the limit placed by 
the specifications"^' of the American Society for Testing Ma- 
terials. 

Sulphuric Acid (SO3). — Portland cement contains usually from 
1.25 to 1.75 per cent, of this ingredient, a large proportion of 
which is due to the admixture of calcium sulphatet with the 
finished cement for the purpose of regulating the setting proper- 
ties. Such additions, however, should not exceed 2 or 3 per 
cent., which is equivalent to about i or 1.5 per cent, of the 
anhydrous sulphuric acid, since an abnormal amount is injuri- 
ous to both the strength and soundness of the product, especially 
if placed in sea water. The standard French specifications limit 
sulphuric acid to i per cent., while American practice is to per- 
mit from 1.5 to 2 per cent. The specifications of the American 
Society for Testing Materials place the limit at 1.75 per cent. 

Sulphur (S). — A small amount of sulphur is sometimes intro- 
duced from the coal in burning, and occasionally from the reduc- 
tion of sulphates in the raw materials. These sulphides cause 
the cement in hardening to become mottled with dark blue spots, 
and if present in appreciable quantities may cause disintegra- 
tion, due to the expansion in oxidizing on exposure to the air. 

Alkalies (K2O and NaoO). — These appear to have but little in- 
fluence on either the burning or quality of the cement. It has 
been held that alkalies acted more or less as a flux in facilitating 
the combination of lime with the silica and alumina, but later ex- 
periments have apparently disproved this theory. Excess of 
alkaHes, under certain conditions, is said to be responsible for 
unsoundness, although this fact has never been (lefinitel\' proven. 
The percentage of alkalies is usually from 0.5 to 2 per cent. 

Carbonic Acid (CO.). — Provided the temperature o{ burning 
has been sufficiently high, the i)resence of (his elenuMit is due 
solely to absorption from the air, and since lime wIumi insntTi 
clently combined is very active in this absorption, an abtK^rniMl 
percentage of carl^onic acid must show either nn(ler])urning or an 

*See Appendix C. 
tSfie paRes 20 and 8,^. 



12 PRACTICAL CEMEXT TESTIXG. 

excess of lime. Normal cements contain from 0.5 to 1.5 per cent, 
of carbonic acid. 

Constitution. — Although Portland cement has been extensively 
manufactured for well over hah" a century, it is only in com- 
paratively recent years that a scientific study of the constitution 
of cement has been undertaken, and even at present the exact 
state of combination m which the different components exist has 
not been definitely ascertained. For many years it was the 
practice to proportion raw materials and to study the finished 
product by means of the "hydraulic modulus," or the ratio of the 
weight of lime to that of silica, alumina and iron, which varied 
between 1.8 and 2.2, but it soon became understood that the 
lime combined in different ratios with the other components, 
and the inadequacy of the formula was thus recog^iized. 

Le Chatelier in 1887 was the first to attempt scientifically to 
explain the constitution of Portland cement.* Following petro- 
graphic methods, and examining with a microscope thin sections 
of clinker and hardened cement, he succeeded in separating them 
into two chief constituents, which later were named by Torne- 
bohm alit and celit. two accessory constituents, belit and felit, 
and in addition an amorphous isotropic mass of matter. He 
considered aht to be composed of tri-calcium silicate, 3 
CaO SiO.. which is the active element in the hardening ot 
cement, and which hydrates as follows : 

3 CaO SiO, - Aq = CaO SiO,2.5 H.O - 2 Ca rOHV 

Cement also contains a tri-calcic aluminate, somewhat un- 
stable, but setting rapidly in water, hydrating according to the 
formula : 

3 CaO ALO, - Aq = 3 CaO Al,0,i2 H,0 

Portland cement, according to Le Chatelier. therefore consists 
of tricalcium silicate mixed v.ith calcium aluminate and ferrate 
and also containing mono and dicalcium silicates. He expresses 
the hydration of cement by the following two reactions : 

2 (s CaO SiO,) - 9 H,0 = 2 CaO SiO, 5 H,0 - 4 Ca (OHV. 
and 

3 CaO ALO, -^ CarOHV, ^ ii H,0 = 4 CaO ALO . 12 H,0. 

•Researches: Expe'-irrentale? Sur la Consrtituiion Des Mortiers Hydrauliques— 
Annalee des Mines — 1SS7. 



COMPOSITION AND CONSTITUTION. 



13 



The calcium tri-silicate is produced by precipitation from a 
^complex silico-aluminate, which permits the combination of the 
siHca and hme. 

He then fixes the amounts of Hme and magnesia in Portland 
ccnents by the expressions: 

Cap + Mg-O ^ 

and ^'^' ^ ^^^^' " ^ 

CaO + MgO > 

SiOs — AI2O3 — FegOs = ^ 

in which chemical equivalents and not weights are used. Good 
commercial Portland cement nearly approaches the maximum 
of the first formula. 

In 1897, S. B. and W. B. Newberry* prepared synthetically a 
number of compounds of silica, alumina and lime, which were 
thoroughly examined, and as a result of their investigations con- 
cluded that the essential constituents of Portland cement are 
tri-cc.lcium silicate with varying proportions of di-calcic alum- 
inate. This composition may be expressed by the formula: 

X (3 CaO SiO,) + Y (2 CaO Al,03) 
or substituting weights for equivalents, the formula becomes 
Lime = silica x 2.8 + alumina x i.i. 

S. B. Newberry statest : "It is understood that this formula is 
merely empirical, representing the relative proportions present, 
since the aluminate remains for the most part in the magma in 
combination with part of the silica and with other substances." 

*Tt should be remembered that this formula represents the 
maximum of lime which a Portland cement, burned in the usual 
manner, may contain without showing unsoundness. This maxi- 
mum can be reached only by extremely fine grinding oi the raw 
material. This formula, also, by no means represents the com- 
position of finished cement, since the ash of the fuel lowers the 
lime and raises the silica and alumina, above that calculated 
from the raw material, by at least 2 per cent." 

'Tn the laboratory, using gas as fuel, it will be found practi- 
cable to prepare sound cements corresponding to tlu- abow for- 
mula. In actual manufacture it is safer to reduce the lime 



♦The Constitution of Hydraulic (VinotitH. by S. H. ami VV. U. Nowborry. Jour- 
nal of tho Society for Dunnical Industry. Vol KI, .\'<). 11. 

tin Taylor and Thompson's "Concrete. Plain and Uoinforced." 



14 



PRACTICAL CEMEXT TESTIXG. 



slightly, to counterbalance possible defective grinding of raw 
material or unavoidable variations in composition. It will be 
found that the raw material at factories where the best Portland 
cements are made rarely falls below the composition, 
Lime = silica x 2./ - alumina x 1.0. 

"This may be taken as a safe practical formula for commercial 
use."' 

In the past live or six years numerous investigators have 
worked on the problem of the nature of Portland cement, and 
many theories as to its constitution and hydration have been 
advanced, although it can be said that none of the essential 
theories based on Le Chatelier's original investigations have 
been positively disproved. 

The subject of the constitution of cement should not be dis- 
missed without allusion to ^Ir. Cliflford Richardson's exhaus- 
tive researches. As a result of the examination of a series of 
synthetically prepared compoimds, he arrives at the conclusion 
that the components of cement are present in a state of soHd 
solution, and that alit and celit, which are the chief minerals 
found in Portland clinker, are com.posed — one of a solution of 
tri-calcic aluminate in tri-calcic silicate, and the other of di-calcic 
aluminate in di-calcic silicate. These, though miscible in the 
molten state, are not so in the solid form. The ratio of alit to 
celit may vary from 3 to i up to 6 to i and possibly over, depend- 
ing on the relation of silicate to aluminate, and on the basicitv 
of the clinker as a whole. 



NOTE:— For further data on this subject, the reader is referred to Mr. Rich- 
ardson's paper on "The Constitution of Portland Cement from a Physico-Chemical 
S»tandpoint.' read before the Association of Portland Cement Manufacturers", 
June 15, 1904. A good resfume of the different theories on the nature of cement 
will be found in a report on "The Manufacture of Portland Cement." by A. V. 
Bleininger— Fourth Series— Bulletin No. ,3— Ohio State Geological Survey. Also a 
review of the literature on the subject prepared by Mr. Richardson was published 
in "Cement"— Volumes 4 and 5— Progress Publishing Company. New York. 



CHAPTER III. 

MANUFACTURE. 

RAW MATERIALS. 

Cement is composed essentially of a mixture of silica, lime, 
alumina and iron, so that any materials containing the proper 
proportions of these ingredients might be employed in the 
manufacture of Portland cement. In fact, Mr. Richardson has 
shown that, theoretically, a true Portland cement may be made 
by substituting other elements of the same groups for those in- 
gredients which are considered to be essential, having made 
actual cements in which alumina is replaced by iron, lime by 
barium, and silica by tin, lead, and even phosphoric acid. From 
a commercial standpoint, however, only a limited variety of 
materials are adaptable. 

The raw materials employed in the Portland cement industry 
in the United States may be divided into six classes : 

(i) Cement Rock and Limestone. — Cement rock is an argilla- 
ceous limestone, low in magnesia, occurring chiefly in Lehigh 
Co., Pennsylvania, and Warren Co., New Jersey, although occa- 
sionally found elsewhere, as in the Virginias. Its composition 
averages from 35 to 40 per cent, of lime, and from 18 to 20 per 
cent, of silica. To produce Portland cement, an admixture of 
from 10 to 30 per cent, of pure lirnestone is generally required, 
although some manufacturers in the Lehigh District are so fortu- 
nate that they are able to make a proper mixture from difforciu 
strata of rock occurring in the same quarry. About two-thirds 
of the Portland cement produced in this country is made from 
this combination of raw materials. 

(2) Limestone and Clay. — These materials are most extensively 
employed in New York State, where clays averaging in com- 
position about 55, 25 and 10 per cent, of silica, alumina and lime 
respectively are mixed with nearly j)ure limestone, the average 
mixtuie being about 20 to 30 ])arts of clay to kx) parts oi lime- 
stone. 

(3) Marl and Clay. — Marl is a soft, wet, calcareous earth. 



l5 PRACTICAL CHMEXT TESTING. 

almost a pure carbonate of lime, usually origmating from shell 
deposits, although sometimes existing as the result of a chemical 
formation. It is found chiefly in the States of Ohio, Indiana and 
Michigan, but also occurs in New York and other localities. 
As widi the second class, it generally requires an admixture of 
from 20 to 30 per cent, of clay. The ease with which the marl is 
excavated and reduced is the economical feature of this process, 
but this is counterbalanced by the handling of a large amount 
of water, and by the increased fuel consumption required for the 
burning of a wet mixture. 

(4) Chalk and Clay. — This combination of raw materials is 
employed extensively abroad, but only to a limited extent in 
this country. Pure chalk, in fact, is never used in the United 
States, but a soft, chalk-like limestone, occurring principally 
in South Dakota, Arkansas and Texas, mixed with clay, is em- 
ployed in a few mills. 

(5) Slag and Limestone. — Certain blast furnace slags granu- 
lated and mixed with limestone may be burned to produce a 
true Portland cement. In Europe, slag has been utilized for 
this purpose for several years, but the process has only recently 
been introduced into this country. Sabin states* that, "whereas 
for the manufacture of slag (i. e., pozzuolana) cement, only the 
slag from gray pig iron is available, it is found that in most 
cases the slag from white pig iron may be used for the production 
of Portland cement from slag." 

(6) Alkali-Waste and Clay. — These materials are used by a 
^Michigan plant for the making of Portland cement, the waste 
occurring from the manufacture of soda by the ammonia-soda 
process, and existing as caustic lime, which is mixed with a 
suitable proportion of clay. 

The average composition of these diiTerent groups of raw 
materials is shown in Table \\, while Table \l. shows the ex- 
tent to which each group is employed in the industry of this 
country. 

The prime requisites for the suitability of any combination of 
materials are that the content of lime, silica and alumina is such 
that the resulting cement will contain these ingredients within 
the limits given in Chapter II. ,t that the percentage of mag- 

*In "Cement and Concrete," by L. C. Sabin, p. 22. 
tSee page 7. 



MANUFACTURE. 



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l8 PRACTICAL CEMENT TESTIXG. 

nesia and ferric oxide in the finished product will be less than 
3 and 4 per cent, respectively, that the content of sulphur be as 
low as possible, not over i per cent, in any form, the presence of 

TABLE VI. — Showing Production of Portland Cement from Various Materials. 

(From article by E. C. Eckel, in Eng. News, April 16, 1903 ) 

Cement Rock and t Limestone and 

Limestone Clay 

Barrels pjg^^^^^^ Barrels p^o^ta^^^ 

1898 production 2,682,304 74.9 315,608 8.8 

1899 " 4>oio, 132 70.9 458,000 8.1 

1900 " 5,919,629 70.3 874,715 10.4 

1901 " 8,503,500 66.8 1,710,773 13.5 

1902 " 10,600,000 67.9 2,100,000 13.5 

*Marl and Clay Chalk and Clay 

Barrels p ^ota^^ Barrels pj^nt. 

1898 production 545,372 15.2 39,000 1. 1 

1899 ♦' 1,095,934 19.4 88,200 1.6 

1900 " 1,444,797 17. 1 184,400 2.2 

1901 " 2,001,200 15.8 495,752 3-9 

1902 " 2,200,000 14. 1 700,000 4.5 

* Including also the product from alkali waste and clay, 
t Including also the product from slag and limestone. 

sulphides being particularly injurious, and that they are free 
from sand or silica in such a form that it will not enter into 
proper combination. 

Calculation of Mixtures. — Since the composition of Portland 
cement can only vary between very close limits, it is evident that 
the chemical laboratory plays a most important role in the pro- 
cess of manufacture. Analyses of the raw materials, of the 
mixture before burning, and of the finished product are made at 
least once a day, and generally more often. 

In starting a mill, or experimenting on new materials, formulas 
such as Newberry's* are frequently employed to proportion the 
mix. As an example, suppose it was desired to obtain the 
proper mixture of cement rock and limestone, analyzing as fol- 

Cement Rock. Limestone. 

Silica (SiOa) 19. i 2.0 

Alumina (AI2O3) 4.5 0.6 

Lime (CaO) 38.8 53.3 

Other ingredients 37.6 44.1 

loo.o loo.o 

the formula being. 

Lime = 2.7 silica + 1.0 alumina. 



^See page 14. 



MANUFACTURE. ig 

The silica and alumina in the limestone require 2.7 x 2.0 + 
i.ox 0.6 = 6.0% lime, which, subtracted from 53.3, leaves 47.3% 
available for combination. 

The silica and alumina in the cement rock require 2."/ x 19.1 
+ i.o X 4.5 = 56.1% lime, but as only 38.8% is present, 17.3 
parts of silica and alumina are unprovided for. 

100 parts of cement rock will therefore require 17.3 x 100 
-f- 47.3 ^ 36.6 parts of limestone. 

Several other formulas,* including the hydraulic index,t are 
also employed for this purpose. In the actual control of a 
mill, however, it is customary, provided the run of the materials 
is fairly uniform, to proportion by the percentage of lime alone. 
Suppose it has been found by experience that the best results 
are produced from a mixture containing 75% carbonate of lime, 
and that it is desired to obtain the proper mixture of a clay, 
and a limestone, containing 24% and 91% carbonate of lime 
respectively. It is then obvious that 91 — 75 = 16 parts of 
clay, with 75 — 24 = 51 parts of limestone, or 31.4 parts of 
clay to 100 of limestone will give the proper mixture. The 
same method of course applies equally well when the oxides in- 
stead of the carbonates are known. 

Occasionally mixtures are proportioned from the percent- 
ages of silica, because of the greater ease with which this in- 
gredient is determined chemically, but the method is much less 
accurate and is apt to give unsatisfactory results. 

PROCESSES. 

The various processes by which Portland cement is manu- 
factured are commonly classified as dry or wet according to 
the method by which the raw materials are mixed and rcchicod, 
while a second classification divides them into rotarv or sta- 
tionary kiln processes according to the manner of burning. 
Each one of these methods cor.sists essentiallx of three steps 
— the mixing and grinding of the raw materials, the cal- 
cining of the mixture, and the final pulverization of the chnkor, 
the last of which is practically the same no matter what process 
is used, although the actual a])])liances may be very ditTcrent. 

♦For diaoussion of several formulas on ceniont batch calcuIntiiMi <he roailor la re- 
ferred to "The Manufacture of Portland l^Mnent." by A. V. Ml.Mi\inKer-Fourth 
Series—Bulletin 3— Ohio State Geological Survey. 

tSee page Hi. 



20 



PRACTICAL CEMENT TESTING. 



The details of manufacture, however, vary considerably in dif- 
ferent localities and are dependent both on the nature of the raw 
materials and on other local conditions, so that although the 
general methods are subject to classification, the details are 
rarely alike in any two mills. 

Dry Process With Rotary Kilns. — This process is adaptable 
to anv class of raw materials vvhicb can be mined and reduced 




Fig. 2 — Spindle Crusher of the Gates Type. 

in a dry condition. The cement-rock and limestone mixtures 
employed in the "Lehigh" district, as well as most of the lime- 
stone' and clay cements are, in this country, treated almost ex- 
clusively by this process, over 80 per cent, of the American 
production of Portland cement being manufactured in this man- 
ner. In brief, the process is as follows : 

The raw materials, after being mined or quarried, and con- 
veyed to the mill, are first passed through crushers, either of 
the jaw or spindle type (Fig. 2), and reduced to a maximum 



MANUFACTURE. 



21 




Fig. 3. — Rotary Drier of the Cummer Type. 

diameter of 2 or 3 inches, after which thev are sent to storage 
bins, where they are kept until their chemical composition 
has been determined so that the mix may be properly pro- 
portioned. The suitable mixture is then made on scales, which 
commonly are of the automatic type, and conveyed to a drier 
which is maintained at a temperature sufficient to drive off the 




¥iG. 4 —Ball Mill of the Krupp 1 > pt\ 



22 



PRACTICAL CEMEXT TESTING. 



greater part of the moisture contained in it. These driers are 
usually built in the form of a rotating cylinder (Fig. 3) 4 or 5 
feet in diameter, 40 or 50 feet long, and slightly inclined to the 
horizontal, the materials entering at the upper or stack end, 
and being discharged hot at the lower end. A small furnace 
usually furnishes the heat, although it has often been attempted 
to utilize the waste hear from the kilns. 

From the drying cylinder, the materials are conveyed to a 
preliminary grinding machine of which the ball mill is the most 
common type, where they are reduced to a size small enough to 
pass a 20 or 30-mesh screen. The ball mill (Fig. 4) consists 
essentially of a revolving drum 5 to 8 feet in diameter, contain- 




FlG. 



-The Komiuuter. 



ing a charge of 3 to 5-inch steel balls, the periphery of the drum 
being made of perforated plates, overlapping each other, 
through which the ground material falls on screens, that of 
sufficient fineness passing through to a hopper, w-hile the tail- 
ings return to the grinding chamber through the spaces between 
the plates. Other forms of preliminary grinding machines are 
the "Kominuter'' (Fig. 5), an improved form of ball mill; rolls 
(Fig. 6) in which the crushing is performed between two rolls 
revolving towards each other and pressed together by heavy 
springs and the ''Kent" mill (Fig. 7) which consists of a re- 
volving ring with three rolls pressing agamst its inner face, 
the material being held to the tire by centrifugal force. Dis- 



MANUFACTURE. 



23 




ADJUSTING 
SCREW. 



Fig. 6. — Buchanan Crushing Rolls. 

integrators of the hinged hammer type are also occasionally cm- 
ployed. 

After the preliniinary grinding, the mixture of raw materials 
is passed to a fine grinder, where it is finally reduced to a size 
such that from 90 to 95 
per cent will pass a No. 100 
screen, or to about the 
fineness of the finished prod- 
uct. The most common 
types of fine gfrinding ma- 
chines are the tube mill 
( Fig:. 8 ) and the GrifTm 
mill (Fig-. 9). The tube 
mill consists essentially of 
an horizontally rotating- 
cylinder t 6 to 24 feet long 
and 4 or 5 feet in di- 
ameter, about half filled 
Vvrith flint pebbles, the 




Vu: 



7— The Kent Mill. 



24 



PRACTICAL C EM EXT TESTIXG. 




Fig. 8.— Tube Mill of the D avidsen Type. 



material entering at the center of one end and leaving at the 
other. Ball and tube mills are commonly arranged in batteries, 
one ball mill supplying sufficient material -for two of the tube 
mills. The Griffin mill is an ingenious device, the grinding 
being performed between a fixed circular tire, and a vertically 
rotating grinding disk suspended from a universal joint, which 
is pressed by centrifugal force against the tire around which 
it turns in a direction opposite to that of its rotation, the fine 
material passing out through vertical screens, while the coarser 
particles are caught up by the shoes under the disk and again 
acted upon. Although these two mills are the most common, 
several other forms may 
be employed. ]\Iills like 
the "Kent'' are some- 
times, in connection with 
an air separator, made to 
perform the final §:rinding-. 
Rolls also may be used 
for this reduction, the 
Edison plant employing: 
this form of g-rinder ex- 
clusively for both crushing: 
and pulverizing:. 

This method of hand- 
ling the raw materials is 
frequently varied, chief- 
ly in two particulars : 
First, when raw materials Fig. q.— Griffin Mill. 




MANUFACTURE. 



25 



of similar texture, such as cement-rock and limestone, are em- 
ployed, the mixture is often made prior to the preliminary 
crushing so that the materials are never handled separately, 
and, second, when very dissimilar materials, like hmestone and 
clay, are used they are usually crushed, dried, and coarsely 
ground separately and the mixture made only before passing to 
the final grinding„ Clay and marl may be handled by this last 




Fig. 10. — Cross-Section of a Rotary Kiln. 

method, although the wet process has usualh been found more 
economical for this combination. The distinctive features of 
the process, however, are similar for all materials. 

From the grinding machines the mixture is conveyed to bins 
above the rotary kilns into which it is fed automatically. The 
rotary kiln (Figs. 10 and it) is a steel cylinder varying in 
length from 40 to 150 feet, and from 4^ to 9 feet in diameter, 
lined with from 6 to 12 inches of fire-brick, inclined 8 or 10 




Fig. II. — Rotary Kiln as Made by The Bonnot Co. 

degrees to the horizontal, and arranged to rotate .u .1 >|K*.d 
averaging about one turn per miiuUe. The raw materials enier 
at the upper end in the form of a powder and in passing through 
are calcined to a clinker which leaves llie kiln in small balls 
ranging from i^ inches to i-inch in diaiiuter. Vhc Inel gener- 
ally employed is hnely i)()\V(lere(i gas slack coal. alth«)ugh both 
oil and ])r()ducer gas have also been used. The coal is blown 
iiUo the lower end of the kiln bv a tan or conii)rcssctl an- and 



26 PRACTICAL C EM EXT TESTING. 

instantly ignited, forming a flame which reaches from 15 to 
25 feet into the kiln, and which creates a temperature of from 
2,600° to 3,000° Fahr. The pulverization of the coal is per- 
formed in tube or "Griffin" mills or in disintegrators, after hav- 
ing first been dried, and is so finely ground that about 90 per 
cent, will pass a Xo. 100 sieve. The temperature of burning, 
and the time required for it vary considerably with the charac- 
ter of the materials and of the fuel as well as with other condi- 
tions, but the temperature will average about 2,700° or 2,800° 
Fahr., while about half an hour is the average time required 
for the materials to pass through an ordinary kiln of about 60 
feet in length, ^^'ell burned clinker is of a greenish black color, 
of a licney-combed structure showing traces of fusion, and is 
fairly uniform in size. 

On leaving the kiln, the clinker is sprayed with a small 
stream of water which both cools it, and makes it more easy to 
pulverize, and then is passed through coolers which reduce the 
heat to normal. These coolers are either constructed in the 
form of a revolving cylinder, similar to the driers for raw ma- 
terials, the clinker passing through against an air blast, or in 
the form of a vertical stationary cylinder through which the 
clinker works its way down over a system of baffle plates 
against a strong current of air. After cooling, the clinker 
should be stored for some little time before the final grinding, 
since the seasoning of the expansives is apparently most active 
at this time. 

The final reduction is efifected by passing the clinker through 
batteries of coarse and fine grinding machines such as ball and 
tube mills, rolls and Griffin mills, Kent and tube mills, or some 
similar combination of these pulverizers. Recourse is freqtient- 
ly made to air separation of the powder, as an economical fea- 
ture of the process, and, with these separators, mills such as 
the Kent may be used alone for the final reduction, thus dis- 
pensing with the second machine. The finished cement, finally, 
is conveyed to the stock house and, after a further storage, is 
packed in bags or barrels for shipment. 

The "addition of sulphate of lime, either in the form of gyp- 
sum or plaster of Paris, is usually made while the cHnker is 
passing from the coarse to the fine grinding machine, although, 
in some mills, the admixture is made in the stock house, nnme- 



CO 
CO 

LU 
O 

o 

DC 
0. 

> 

cc 

Q 
LU 

X 

I- 

o 

z 

■5= =^ 

Z «M 

LU o 

UJ 

O 

D 
Z 
< 

-J 
H 

GC 
O 

Q. 



MANUFACTURE. 27 

diately before packing. The first of these methods secures a 
more thorough mixture, although the sulphate is apparently 
more effective when the latter method is followed, the long 
storage at the high temperature of the bins seeming to affecL 
its activity. 

The plan of the cement mill shown in Fig. 12, illustrates th-.: 
general lay out of the various machines and appliances used in 
this method of manufacture. The dry process with rotary kilns 
may be considered the typical American method for the manu- 
facture of Portland cement. 

Dry Process With Stationary Kilns. — This method, at one 
time, was largely employed in the United States, but has how 
been almost superseded by the rotary process. The advantage 
of the process is the reduced fuel consumption, which, however, 
is usually more than off-set by the increased amount of labor 
required. The relative economy of the two processes thus de- 
pends upon the relative cost of fuel and labor, in this country 
the rotary process being generally found the more economical, 
while, in certain foreign countries, the high cost of fuel com- 
bined with the cheapness of labor, often creates the reverse 
condition. The quality and properties of the cement made by 
the two processes are very similar, although that produced in 
rotary kilns is apt to be more uniform. 

In this method, the raw materials are mixed, dried and ground 
in a manner similar to that already described, but after tlic 
final grinding the material is passed through a pug mill where 
it is mixed with a small amount of water, then pressed and cut 
into bricks or cubes, the process being very similar to that em- 
ployed in the ordinary making of building brick, after which 
they are sent to drying tunnels where they are dried and 
hardened. 

From the tunnels, the bricks are taken to the kilns where 
they are burned to a clinker. The more uneven character of 
the burning in stationary kilns usually makes iniixM-ative a 
sorting of the clinker, and a discarding of that which is eitluT 
under or over burned, after which the process is similar to that 
employed with rotary kilns, except tliat the larger si/c (^f the 
clinker usually rec|nircs a preliminary rough crushing bef(M-o 
it is sent to the grinding machines. A plan o^ a cement mill 
using" this proctv^s is shown in Fig. 13. 




FIG. 12. PLAN AND SECTION OF A PORTLAND CEMENT MILL USING THE DRY PROCESS WITH ROTARY KILNS. 



28 



PRACTICAL CEMENT TESTING. 



vStationary kilns are of three general t>pes — the dome kiln^ 
the continuous or shaft kiln, and the ring or chamber kiln. 
The dome kiln consists of a single shaft in the form of an in- 
verted bottle in which the bricks of cement materials and the 
fuel, usually in the form of coke, are placed in alternate layers, 
and then fired and burned. After cooling, the clinker is drawn 
from the bottom, sorted for the purpose of discarding that 
poorlv burned, and then ground to cement. The use of this 
kiln is uneconomical in the heat wasted wdien firing and when 
cooling, and also in the comparativeh small output, due to the 



Brick Furnace 




pmS^WAim 




Fig. 13. 



-Plan of the Works of a Portland Cement Plant Employing Stationary 
Kilns. 



intermittent character of the operation. The burning also is 
much more difficult to control so that the poorly calcined clinker 
amounts to a considerable proportion of the output. Its use is 
commonly limited to mills of very small capacity. 

Continuous or shaft kilns are of several types, among which 
the Aalborg, Dietzsch and Schoefer are the best known, but 
are all similar in that they consist of a tall vertical shaft into 
the upper part of which the materials and fuel are charged in 
alternate layers, while the finished clinker is drawn from the 
bottom. Alost of these kilns are contracted near the center at 
the point where the temperature reaches its maximum. The kiln 
illustrated In Fig. 14 is an American adaptation of the Schoefer 
type used in one of the few mills that still follow this process. 



MANUFACTURE. 



V 



Ring or chamber kilns consist of a series of chambers ar- 
ranged around a central stack in such a manner that while the 
materials are being burned in one chaml^er the exhaust heat 
passes through the other chambers, thus raising the tempera- 
ture of the materials about to be burned. This svstem is well 




Cross -Section through Kiln. Elevation. 

Fig. 14. — Continuous Kiln of the Schoefer Type. 

known in the l)rick in(histr\-. but is not emi)lo\c(l in lhi> coun- 
try for the burning of cement. 

Discussing the relative economy of (h)mc and cotiiinuous 
kilns as compared witli those of the rotarv t\])e, .\Ir. !•". II. 
Lewis, in "The Cement Industry," gives tlu- following data: 

Quantity of fuel re(|uired i)er dav : 

Intermittent kilns i 5 l<i ,^0 barrels. 

Contimunis shaft kihis 40 lo Sobarrel.s. 

Rotary kilns ijo to 250 barrels. 



30 PRACTICAL CEMENT TESTING. 

Ratio of fuel consumed to clinker produced : 

Intermittent kilns 25 to 35 per cent. (coke). 

Continuous shaft kilns 12 to 16 per cent. (coal). 

Rotary kilns 30 to 40 per cent. (coal). 

Comparison of cost under American conditions : 

Continuous 
Rotary kiln. shaft kiln. 

Labor cost per barrel 2^ to 4 cents. 12 to 14 cents. 

Fuel cost per barrel 11 to 15 cents. 5 to 6 cents. 

Wet Process With Rotary Kilns. — In the United States, this 
process is utiHzed only by the mills (see Fig. 15) operating on 
marl, with the exception of the one mill which utilizes the waste 
from the manufacture of soda, but it also may be applied to 
any other raw materials, such as chalk, that exist in a finely 
divided state, although not excavated in a wet condition. As- 
suming the use of marl and clay, the process is as follows : — 
The marl, after excavation, is passed through a disintegrator 
and sometimes a stone and grass separator, and run into stor- 
age basins, while the clay is dried, pulverized, and then mixed 
with a proper amount of marl in pans of the edge runner type 
(Fig. 16), the slurry containing enough water to give it a thick 
creamy consistency. In some mills, this process Is varied by 
mixing the clay with water before adding it to the marl. The 
mixture then is ground, while still in a wet condition, in either 
edge runners or tube mills, from which it is run into slurry 
tanks where it is kept agitated by revolving paddles or by com- 
pressed air, and where chemical analyses are made to check 
the accuracy of the proportions, corrections being made if nec- 
essary. Centrifugal pumps and compressed air are both used 
for handling the slurry. 

The wet slurry is then pumped directly into the upper ends 
of rotary kilns which usually are somewhat longer than those 
employed in the dry process so that the waste heat may be 
utilized in driving ofif the excess water. About 150 to 160 
pounds of coal per barrel of cement are necessary for the 
burning, which is 30 to 50 per cent, more than Is required In 
the dry process, but this disadvantage is largely compensated 
by the cheaper method of handling and preparing the raw ma- 
terials. The treatment of the clinker is similar to that of the 
other processes. 







PLAN OF THE WORKS OF A PORTLAND CEMENT MILL USING THE WET PROCESS. 
(To face page 30.) 



MANUFACTURE 



.V 



Wet Process With Stationary Kilns. — llris process also is 
only adaptable to soft, wet, or finely divided materials. The 
clay and marl, or chalk, are first ground, if necessary, and then 
mixed together in a wash mill with a large excess of water, 
the lumps being broken up by means of agitators. When the 
materials have thus been reduced to a very finely divided state 




Fig. i6. — Mixinj,' Pan for Marl and ("lay. 

the mixture is run. into settling basins, when the solid matter 
settles and from which the excess of water is drawn otY. The 
slurry when still further hardened is then formed inm bricks, 
and l)urned in stationarN kilns. 

A modification of tin's method, known as tlu- semi wet 
process, consists in mixing with a smaller amount of water, 



2^2 PRACTICAL CEMENT TESTING. 

sufficient to give a creamy consistency, tlie operation being 
similar to the wet process with rotary kilns except that the 
slurry is partly dried and formed into bricks instead of being 
fed directly into the kilns. 

The chief disadvantages of the process are the large space 
necessary for settling and drying the slurry, and the greater 
amount of labor required. It, however, is used extensively in 
Europe, and in England a few years ago might have been con- 
sidered the typical process. In this country, cement is not 
made by this niethod. 

Portland Cement From Slag. — The only other distinctive 
process employed in the United States is in connection with 
the utilization of blast-furnace slag. The slag immediately after 
leaving the furnace, is sprayed with a stream of water which not 
only granulates it, but also drives oft the sulphur, changing 
the calcium sulphide into calcium oxide and hydrogen sulphide 
which is evolved as gas. The slag is then dried, ground, mixed 
with the proper amount of ground limestone and burned in 
rotary kilns, following the dry process. 

Essentials to Good Manufacture. — From the standpoint of the 
production oi well-made material, in contradistinction from that 
of economy, the essentials to good manufacture are : 

(i) Proper raw materials ; so that a mixture containing the 
correct proportions of silica, lime, alumina and iron may be 
made from them, and also containing but a small percentage 
of the injurious constituents notably magnesia, sulphur, and 
the alkalies. 

(2) Correct proportioning ; it being impossible to produce 
good cement from an incorrectly proportioned mixture. 

(3) Fine grinding of the raw materials. When the raw ma- 
terials are calcined, the formation of the dififerent constituents 
of cement takes place by a process of dififusion. so that only 
those particles which exist in a very finely divided state are 
capable of combining properly. The most common cause of 
unsoundness in cements is insufficient grinding of the raw ma- 
terials. 

(4) Proper burning. If the temperature of burning is too 
high or too low, or if the duration of the calcination is 
either lengthened or shortened, the character of the product 



MANUFACTURE. 33 

will be vitally affected, and if varying beyond a very limited 
range the material suffers exceedingly in quality. 

(5) Sufficient storage. Both the clinker before final grind- 
ing and the finished cement should be kept in storage for a con- 
siderable time in order that any expansives that may be pres- 
ent will have sufficient time to absorb water and carbonic acid 
and thus become inert. Most cements require from 2 weeks 
to a month for this action to take place, and should never be 
used in less than that time. As a rule, the more finely the raw 
materials are ground, the less time is necessary for storage. 



CHAPTER IV. 

IXSPECTIOX AXD SA.MPLIXG. 

Reception and Storage. — Portland cement is shipped from the 
manuiacturers to the site of the construction work either in 
barrels of wood or in bags of cloth, canvas or paper, the net 
contents of four oi these bags equaling that of a barrel. Ship- 
ments intended for distant points, especially when carried by 
water, are usually sent in wood, but under ordinary condi- 
tions bags are generally employed. In other words, barrels 
are employed when the material may be subjected to excessive 
dampness, or when it v.ill not be used for a considerable time, 
since the cement is berter protected when thus packed, but, on 
account of the much greater ease in handling as well as be- 
ing more economical, bags are used whenever it is practicable. 
From S5 to 90 per cent, of the domestic product is shipped 
in bags. 

The common cloth bag has the advantage of being adapt- 
able to much rougher handling without danger of destroying it, 
but on the other hand paper bags are cheaper and have the 
additional advantage of being broken and so rendered unfit 
for filling a second time after the material has been removed, 
and thus make rebagging on the part of local dealers impossi- 
ble. Owing to the fact, however, that the paper bags are often 
broken in transportation and in handling on the work they are 
justly rather unpopular and hence used but infrequently. The 
danger of allowing an unprincipled dealer to rebag an inferior 
quality of cement in packages marked with a standard brand 
may be obviated by requiring the manufacturers to seal each 
of their bags with a wire and stamped lead seal, which is de- 
stroyed when the package is opened. The additional expense 
of this sealing is insignificant, and should be required on any 
important piece of construction where the material is not pur- 
chased from the manufacturers directly, and when sufficient 
facilities for testing are not at hand. 

It is customary to inspect and test cement after it has been 
received on the site oi construction, both as a matter of con- 



INSPECTION AND SAMPLING. 



35 



venience, and to ensure against the substitution of inferior ma- 
terial after inspection, although the practice on two or three 
of the most important engineering works, notably that of the 
New York Rapid Transit Subway, has been to inspect the ma- 
terial in the stock house at the manufacturers. For works 
using an extremely large quantity of material produced at a 
single mill this may be advantageous, but otherwise it is im- 
practicable, and furthermore is less accurate for the reason that 
the conditions surrounding the cement during transportation 
may be of such a nature as to alter its physical properties com- 
pletely, so that the material tested is radically different from 
that used. 

The specifications for the reception of cement shipments 
usually stipulate a definite time, never less than eight or ten 
days, during which they must be held on the work wdiile un- 
dergoing test, and this necessitates ample facilities for storage. 
The principles for storing cement properly are first to protect 
it from dampness or excessive heat, and secondly to allow the 
access of as much dry air as possible. Cement is generally 
received in car-load shipments of from lOO to 150 l)arrels, and 
it is convenient to inspect, test and store the material in these 
car-load lots. Store houses, therefore, should be divided or 
partitioned into a number of bins, each being of size sufficient 
to hold one car load and so arranged that each bin is readily 
accessible so that it may be filled or emptied w^ith a minimum 
amount of labor. Over, or by the side of each bin, shciuld be 
placed a board or placard on which is written the brand of 
cement, the number of packages, the name and number of the 
car in which it was shipped, and the date when received, and 
after test should be marked accepted or rejected, with the date. 
Rejected material should be removed at once under the super- 
vision of an ins])ector, and some or all of the packages marked 
with a private mark so that it can be recognized if attemj)! is 
made to ship it back again. 

When using standard brands of cement with whicli \\\c en- 
gineer has had consi(leral)lc experience, a seven-(la>- test is 
usually sufificient. New or unfamiliar brands should, hcnvever, 
never be accepted on less than a twenty-eight -da \ lest. (."iMueut 
failing in certain tests may, by reason of the additional season- 
ing gained in two or three weeks, pass those tests at the expira- 



36 PRACTICAL CEMEXT TESTIXG. 

tion of tliat time, so that the retesting of cement failing in the 
first tests is perfectly justifiable in certain instances, and, more- 
over, the fact that there may be a wide discrepancy between the 
results of the two series of tests need not necessarily cast dis- 
credit on the laboratory . 

Inspection. — The field inspection of cement shipments should 
include an examination of the condition of the packages and 
of the material, examination of the storage faciUties, and, it 
required, a determination of the average weight of the pack- 
ages. 

The packages should each be plainly marked with the brand 
and name of the manufacturer; unbranded packages should 
be discarded and not allowed to enter the work. They should 
be in fairly good condition, securely tied, and, if so stipulated 
in the specifications, sealed properly with a lead seal. In case 
the seal and brand mark bear different names, the name on 
the seal should govern, but this should not be allowed to occur 
except in occasional instances. 

Regarding the condition of the cement as a whole, the field 
inspector often is able to form a more correct judgment than 
the tester in the laboratory. Old or well seasoned cement gen- 
erally appears rather lumpy, but these lumps can easily be 
crushed in the fingers and hence in making the mortar or con- 
crete are entirely broken up and thus are not detrimental. If 
the material, however, has been subjected to excessive damp- 
ness, or has actually been wet, lumps are formed, similar in 
appearance to those occurring in old cement, but are hard and 
can only be crushed by the exertion of considerable force. Al- 
though when a concrete machine mixer is used these lumps 
may be well broken up, the cement in them is, nevertheless, par- 
tially hydrated and hence inferior. In hand mixing the making 
of a smooth mortar from such cement is almost impossible. 
Material containing lumps of this character is occasionally 
screened and the siftings used, but even then the finer particles, 
which must have been subjected to nearly the same conditions as 
those that formed lumps, cannot be of as good a quality as 
originally. It is, therefore, usually advisable to reject out^ 
right a shipment containing any appreciable quantity of these 
hardened lumps, unless, of course, the conditions producing 



INSPECTION AND SAMPLING. 



55? 



this result only affect a certain part of the shipment, in which 
case only that part need be rejected. 

The color of Portland cement"^' affords no criterion of quality 
in field inspection, except in so far as uniformity is concerned. 
If it IS observed that the contents of different packages are 
different in color, it is obvious that the shipment is not ail of 
the same material and tests should be made from separate 
packages to ascertain whether the cement is all acceptable, or 
whether it is a mixture of good and bad material. 

The store-house should be inspected to see whether the 
material is properly protected, so that it is impossible for the 
cement to deteriorate in quality while it is being held. It fre- 
quently happens that a shipment may show^ excellent tests but, 
by the time of their completion, the material has been so mis- 
handled as to have become worthless. 

A provision of many cement specificationsf is that the net 
weight of the packages shall no: be less than a certain fixed 
quantity. This determination being made in the field is con- 
sidered as part of the inspection rather than the testing and 
consists of weighing, say lo packages, either separately or to- 
gether, and then the bags or barrels after the material has been 
emptied from them, the difference being the net weight of the 
packages. 

A full report of the lield inspection of every shipment should 
be sent to the testing laboratory with the sample and made a 
part of the permanent records. 

Sampling. — The maximum size of a shipment of cement 
which can be represented by a single sample for testing, is a 
matter governed more by local conditions and the discretion 
of the engineer than by any fixed rules. In practice, since cement 
is usually shipped in car-load lots of lOO to 150 barrels, it is 
convenient to represent this quantity by a single sample, but 
this (|uantity is near to the safe maximum, so if a lot oi ce- 
ment exceeds 150 barrels, it is advisable to separate it into por- 
tions of not over this amount, and to sample each porti(in sepa- 
rately. 

The sample for testing is generally taken in .^ne ot three 
ways: (t) An average sample from sevend packages: (2) 

♦See page 10. 
tSee Appendices. 



38 PRACTICAL CEMEXT TESTING. 

separate samples, each from a single package, tested separate- 
ly ; (3) from a single bag taken at random. 

A sample taken from only one bag is manifestly unfair and 
inaccurate and the method hence should never be permitted. 
The separate testing of a number of samples, each taken from 
a single bag, involves usually a large amount of unnecessary 
work, especially if the lot represents a shipment of not more 
than 150 barrels. AMien a shipment of about 1,000 barrels is 
received the method may be employed, but even then it is pref- 
erable to subdivide the shipment and test an average sample 
from each portion. Occasionally, however, the testing of such 
samples may be desirable, especially with a new brand, as a 
check on its uniformity . The inspectors of the cement intended 
for use in the Xew York Rapid Transit Subway make their 
test<^ at the mill on eleven samples taken from each bin, ten of 
^vhich are from borings made at different parts of the bin while 
the eleventh is a mixture of the other ten. For the usual con- 
dition, however, of shipments received in lots of 150 barrels or 
less, a single sample representing the average of the material 
is sufficient. 

The proper number of bags to sample necessarily depends 
largely on local conditions which cannot be formulated. The 
Committee of the American Society of Civil Engineers""^ rec- 
ommends that "where conditions permit, one barrel in every 
ten be sampled," and since four bags equal a barrel, this is 
equivalent to sampling one bag in forty. Although this amount 
is representative of average practice for larger lots, it is entire- 
ly too little for the small lots frequently received for short sec- 
tions of sewer and other similar small jobs that are common in 
municipal work, where the entire amount of cement used may 
be only 30 or 40 bags, and which according to this method 
would be represented by a sample from only one bag. The 
author's practice is to sample 5 bags for every 50 barrels or 
less in the shipment, which agrees with the Committee's recom- 
mendation for large lots, but never permits less than 5 bags 
to be sampled. 

In selecting the packages to be sampled, care should be ex- 
ercised that they are taken from different parts of the pile and 
so fairly represent the average of the shipment. If it is possi- 
ble, the best time to take the samples is when the cars are being 

*See Appendix A. 



INSPECTION AND SAMPLING. 



39 



unloaded at the store-house, every bag- in thirty or 
forty being- opened and sampled. 

The size of the samples depends on the number of 
tests to be made ; for the ordinary tests as given in 
any one of the standard specifications, the amount 
should be between 8 and lo pounds. 

The material taken from any one package should 
also be an average of its entire contents, since the 
cement on its exterior is more' liable to influences 
operating- to change its properties than that on the 
interior, and also on account of the separation 
of coarse and fine particles in cases where the package has been 
subjected to much jolting in transportation. In sampling a 
barrel, a hole should be made in one of the staves midway be- 



FiG. 17. — 

Sampling 

Auger. 



i_3 



Fig 18. — Can for Collecting Samples. 

tween the heads, and material removed from the center to the 
side. A sampling auger, or "sugar trier" (Mg. 17) is con- 
venient for this purpose. A bag should also be sampled from 
surface to center, using either the auger or a long narrow 
scoop. 

For collecting samples, the author uses the form of can 
shown in Fig. 18, which is divided into four compartments, the 
upper two of which are in a removable tray, the dimensions «>t 
the can being 14^^ inches x 5 inches x 8 inches, and each com- 
partment holding al)ont 8 pounds of cement. Two of these 
cans are as nuich as a man can carr\ with comton. When the 
samples are brought to the hdx^ratory. they are emi)tied into 
a paper wash basin, thoroughly nnxed with a spoon or trowel. 



40 



PRACTICAL CEMENT TESTING. 




Fig. 19. — Sample Cans. 



then poured into sample cans similar to those in Fig. 19, ex- 
cept that they are provided with handles. The thorough mix- 
ing of a sample taken from several packages is a proceeding 

that never should be neglected. The 
laboratory of the Philadelphia Rapid 
Transit Co. uses square sample cans 
2/4 inches X 8 inches X 9 inches, and 
for collecting has a cover box holding 
four of these cans. This however 
makes an additional weight to carry 
and has the further disadvantage of not 
requiring the removal of the material 
on reaching the laboratory, thus en- 
couraging the assistants to shirk the trouble of thoroughly- 
mixing it. The square cans also are less easily handled than 
round ones although they take up less space in storage. 

The only preliminary treatment required for the sample is 
in cases when it has become mixed with foreign matter such as 
sticks or stones or splinters from the barrel, or contains 
lumps, in which case it should be sifted through a coarse sieve, 
about 20-mesh, to remove them. This sifting has been recom- 
mended^' for all samples to ensure a thorough mixing, but is 
not necessary nor as efficacious as a thorough mixing with a 
trowel or spoon. 

After placing the cement in the sample can, it should be 
given a consecutive number, tightly covered and placed in a 
dry atmosphere at a normal temperature until tested. Samples 
collected in extremely hot or cold weather should always be 
brought to a temperature of about 70° Fahr. before testing. 



*See Appendix A. 



CHAPTER V. 

THE TESTING OF CEMENT. 

Tests of cement may be divided into two classes — research 
or experimental tests, and routine tests. Those of the first 
class are made for the purpose of determining how the mate- 
rial may be made and used to the best advantage and include 
such tests as investigations on the constitution of cement, de- 
terminations of its physical constants such as the coefficient of 
expansion and the modulus of elasticity, and also such tests 
as those of porosity, adhesion, effect of frost, effect of sea- 
water, and similar investigations which have as their object the 
study of the class of material as a whole. Routine tests are 
those whose purpose it is to determine whether a particular 
shipment of cement is of a quality sufficiently good for use in 
construction work. It is with this second class of tests that 
this book is chiefly concerned. 

For a cement mortar or concrete to give good service in 
actual work it must possess two essential qualities — strength, 
or ability to carry the loads it is designed to sustain, and 
soundness, or ability to withstand any forces, either interior 
or exterior, which tend to destroy its permanency. 

The routine or reception tests to which a cement is usually 
subjected are soundness, tensile strength (both neat and with 
sand), fineness, specific gravity, and time of setting. Other 
tests less [requently used are those of chemical analysis, com- 
pressive and transverse strength, apparent density, shearing and 
adhesive strength, microscopic examinations, etc. 

These different tests may be classified as primary or sec- 
ondary, the primary tests being those of strength and sound- 
ness, which qualities the material must necessarily possess, 
while the secondary tests, including those of specific gravity, 
fineness and chemical analysis, are tiiosc made to give addi- 
tional information as to the ability of the material to c|ualify in 
the primary requisites, and have no intrinsic value in them- 
selves. In the case of the fineness test, for example, no possi- 
ble reason can be given for re(iuiring the cement to be ground 
to a certain point, except that experience and investigations 
have shown that the fine material has qreater strength and less 



42 PRACTICAL CEMENT TESTING. 

liability to unsoundness, but otherwise the actual size of the 
particles can make no difference. 

The determination of the time of setting can hardly be 
placed in either of these classes, for while it bears a relation to 
both soundness and strength, it is made chiefly for the purpose 
of ascertaining whether the material can be conveniently used, 
or that the time when it begins to harden will not be so soon 
that it cannot be properly placed, or so late that it will delay 
the progress of the work. 

It has just been stated that the common test for strength is 
made in tension, while the compressive and transverse strength 
is determined but infrequently. The reasons for this will be 
given in some detail in Chapter IX., but it can be said here 
that although there is and can be no fixed relation between the 
strengths in tension, compression, cross breaking and shear,, 
nevertheless the tensile strength is a comparatively fair meas- 
ure of the abilitv of the m.aterial to withstand the otTier forms 
of stress, and, since it is by far the simplest of the strength 
tests to employ in routine testing, its adoption for this purpose 
is almost universal. The old argument that, since mortar and 
concrete are most frequently subjected to compression, the 
tests should also be so made, has been generally abandoned, 
and as a matter of fact, if the failures of cement constructions 
be studied, it will be noted that almost all of the failures of 
strength are due to weakness in tension, cross breaking or 
shear and rarely if ever to compression. In fact, the cracks 
usually to be observed in heavy monolithic concrete construc- 
tion generally are due to temperature changes or shrinkage, 
the concrete actually failing in tension. 

Development of Testing. — The development of cement testing 
runs more or less parallel to that of production. Smeaton's 
first tests were made by forming small balls of the material, 
placing them under water, and observing their hydrauHc prop- 
erties. 

The first crude strength test was employed by Pasley, about 
the year 1830, and consisted in cementing bricks against a 
wall one at time, the second being cemented to the first and 
so on, the bricks forming a projecting beam, and the cement 
holding the greatest number of bricks being adjudged the su- 
perior. No distinction was made between quick and slow 



TESTING OF CEMENT. 43 

setting cements, and it is not even stated whether or not the 
bricks were added at fixed intervals. Pasley's next test was 
more scientific in its character and consisted of cementing to- 
gether two bricksv^on end and determining the weight neces- 
sary to pull them apart. This appears to have been the origin 
of the tensile test. Pasley also determined the time necessary 
for a cement paste to harden under water. In the light of 
recent investigations on the subject of cement testing and in 
view of the great difficulties encountered by our scientific 
bodies in formulating accurate methods of testing, it is most 
interesting to note that Pasley as a result of his experiments 
endeavored "to lay down rules for judging the quality of ce- 
ment offered for sale and for ascertaining whether it has been 
adulterated or not, by attending to which the most inexperi- 
enced person may easily detect such frauds in twenty-four hours 
or less," and also that "the comparative strength of cements 
may be judged of experimentally, and in a short space of time, 
such as ten days, with very little trouble, and the greatest 
accuracy." 

Meat, in 1828, devised a form of apparatus for determining 
the hardening of cement, consisting of a plunger loaded with 
a fixed weight which fell from a definite height into a cement 
paste, its penetration being a measure of the hardening. A 
modification of this apparatus, known as the Vicat needle, is 
the present standard for testing time of setting. The first ce- 
ment briquettes made in France were molded in the form of 
a rectangle and when hard set were removed from the molds 
and notches cut in them to receive the clips. 

John Grant, in 1858, when making tests of cement in con- 
nection with the construction of the London ^Main Drainage 
Works was the first to place them upon a scientific l)asis. and to 
develop definite methods. The form of bri(|uctto which he 
finally adopted after a long series of investigations is essen- 
tially the same as the English and American standards of to- 
day. His testing machine also was very similar in form to the 
long lever types now generally used. 

Michaelis, in 1870, and Faija, in i8Sh, were the first to in- 
troduce forms of accelerated tests iov soundness. 

Methods of Testing.— The chief reason that it is difficult to 
secure uniform and accurate tests of cement lies in the fact 



44 



PRACTICAL CEMENT TESTING. 



that this material is one in which the tests, or at least the im- 
portant ones, are made on artificially prepared specimens and 
not on the material in the form in which it is manufactured and 
sold. Cement is produced in the form of powder, tested for 
the most part as a paste, and used as a mortar or concrete. A 
specimen of iron, steel, wood or brick is shaped to fit the ma- 
chine in which it is to be tested, but in so doing its physical 
properties remain unchanged, and the only errors that can be 
made are those due to incorrect manipulation of the machine. 
For the important cement tests, on the other hand, it is first 
necessary to prepare the specimens, the making of which com- 
pletely changes the physical and chemical properties of the 
material, and which, therefore, must always be done in an ac- 
curate and uniform manner to produce true results. 

Considered in this light, the ordinary tests of cement may be 
classified as either absolute or relative ; the absolute tests be- 
ing those of specific gravity, fineness and chemical anaylsis, 
which are made on the material as it is produced, while the 
relative tests include those of setting, strength and soundness, 
in which the material is changed both in form and in proper- 
ties before the actual determination is made. It will be noticed 
that the essential tests of strength and soundness both come 
under the head of relative tests, and it is for this reason that 
the other tests are made, to give additional information as to 
the character of the material, for if strength and soundness 
could be determined absolutely there would be no necessity for 
any other tests. 

Since the preparation of the specimens is so important a 
phase of the subject, it is especially necessary that uniform 
methods be followed if the results obtained by different labora- 
tories and individuals are to be comparable. Recognizing this 
fact, committees of scientific societies have repeatedly attempted 
to formulate uniform methods of testing. The various com- 
mittees of the German Association of Portland Cement Manu- 
facturers, and the French Commission of 1891, on Standard 
Methods of Testing the Materials of Construction, have done 
notable work along these lines. In the United States, a Com- 
mittee of the American Society of Civil Engineers, in 1885, P^^' 
duced the first standard for methods of cement testing. These 
rules, however, soon became obsolete so that the same body 
later appointed another Committee which submitted a Progress 



TESTING OF CEMENT. 4- 

Report,^ in January, 1903, which, aUhough by no means per- 
fect, is a distinct advance on anything previously done for 
the promotion of uniformity in the methods of cement test- 
ing. Acting along similar lines, a Committee of the New York 
Section of the Society for Chemical Industry, in 1902, formu- 
lated a standard methodf to be followed in the chemical an- 
alysis of cement. 

Unfortunately, some of the most important operations in 
cement testing cannot be performed mechanically, and this 
furnishes one reason why it is such a difficult matter to formu- 
late uniform methods, since in any process where personal 
equation is an important factor, practical experience is more 
essential than any amount of theoretical training or knowledge. 
In regard to this, the report of the Committee, of 1885, of the 
American Society of Civil Engineers says : 

''The testing of cement is not so simple a process as it is 
sometimes thought to be. No small degree of experience is 
necessary before one can manipulate the materials so as to ob- 
tain even approximately accurate results. 

'The first tests of mexperienced, though intelligent and 
careful persons, are usually very contradictory and inaccurate, 
and no amount of experience can eliminate the variations in- 
troduced by the personal equation of the most conscientious 
observers. Many things, apparently of minor importance, exert 
such a marked influence upon the results, that it is only by 
the greatest care in every particular, aided by experience and 
intelligence, that trustworthy tests can be made." 

Requisites for Good Testing. — The prime requisites for the 
accurate and efficient testing of cement may be summarized as 
follows : 

(i) The operators should be experienced and well-trained 
men, careful and conscientious. 

(2) The various operations should be based upon a stamlaril 
or pre-determined method and no deviations slunild bo tol- 
erated under any pretext. 

(3) The methods should aim at the greatest accuracy and the 
greatest simplicity combined with an expenditure of the least 
amount of time and labor. 

(4) Personal equation should be eliminated as far as possi- 
ble from all operations. 

(5) The records should be as coniiilete as i>ossil)Ie. but not 
unnecessarily complex. 

*9ee Appendix A. 
tSee AppcMidix B. 



CHAPTER VI. 

SPECIFIC GRAVITY. 

Definition. — The specific gravity of a substance is the ratio 
of the weight of that substance to the weight of an equal vol- 
ume of water. Since, in the metric system, the cubic centi- 
meter of water is taken as the basis of the gram weight, it fol- 
lows that the specific gravity of a substance becomes the ratio 
of its weight in grams to its volume in cubic centimeters. This 
determination, therefore, consists of a measurement of weight 
and a measurement of volume. 

TJnderburning. — The specific gravity of a well-burned cement 
is known to have certain definite limits. The higher the tem- 
perature used in burning, the more thoroughly will the in- 
gredients be combined, thus giving by their contraction in vol- 
ume a greater density or specific gravity. An underburned 
cement contains a large proportion of uncombined or insuffi- 
ciently combined elements, some of which are sources of great 
danger, and in use may be sufficient to cause the disintegration 
of the cement, and the failure of the structure. Overburning, 
on the other hand, tends to break up some of the compounds 
which should be present in a normal cement, and to form other 
compounds that, although not generally injurious, are never- 
theless possessed of much more feeble hydraulic properties, and 
thus tend to weaken the material. 

It is thus evident that a normal cement must have been 
burned within a certain small range of temperature, and as the 
specific gravity is a measure of the degree of burning, it fol- 
lows that if the cement be normal its specific gravity must lie 
within definite limits. 

Adulteration. — Another important function of this test is the 
frequent detection of adulterants. Excluding plaster of Paris, 
or gypsum, the use of which is legitimate, the most common 
of the adulterants of Portland cement are raw-rock, slag, cin- 
der, and natural cement, all of which have a much lower spe- 
cific gravity, ranging from about 2.55 to 2.95. If a cement be 
of good quality it is frequently possible to add to it twenty, 



SPECIFIC GRAVITY. ^j 

twenty-five, or even a greater percentage of these materials, 
and, if thoroughly mixed, to have this addition escape detec- 
tion in all of the physical tests with the exception of specific 
gravity, in which test the substitution at once becomes appar- 
ent. For example, if a cement (sp. gr. 3.15) be mixed with 
10% of raw-rock (sp. gr. 2.64), the specific gravity will be low- 
ered to 3.10, and with 25% will be reduced to 3.02, so that an 
addition of even 10% will be apparent to an operator familiar 
with the normal properties of that particular brand. 

The specific gravity test alone, however, should never be 
relied upon for the detection of adulterants, since many other 
causes also may operate to produce an abnormally low value, 
chief of which are the age and the composition of the material, 

TABLE VII. — Effect of Age on Specific Gravity of Cement. 
(From Butler's " Portland Cement.") 

No. 1 No. 2 No. 3 No. 4 

Specific Gravity when received 3 160 3-175 3 160 3 120 

in I month 3.055 3.125 3130 3.109 

" " " 3 months 3095 2.965 3084 2.985 

" " "6 ** 3016 2.930 3018 2.995 

■ "9 " 2.969 2.915 3.015 2.985 



Loss in six months (per cent). ... 4 55 7 7^ 44'* 4.006 

and in a lesser degree the fineness of grinding and the exterior 
conditions under v;hich the test is made. 

Effect of Age. — Cement exposed to the air gradually al)sorb> 
water and carbonic acid which, whether existing in a combined 
or in an absorbed state, materially tend to lower its s])ecific 
gravity. 

Table VII. is taken from a paper read by Henry l'\iija be- 
fore the Society of Engineers, showing the results of experi- 
ments made to demonstrate this action. I'nfortunatclv the 
conditions under which these tests were made are not given, 
but assuming them to be normal the falling off in specific grav- 
ity is unusually great. Such an extreme case as that of No. 2 
in which the specific gravity falls off 0.210 in three months 
could occur but very infrec|uently. Also the fact that in two 
cases an increase is shown jMiints either ti^ peculiar condition.^ 
or inaccuracy in the work. The humidity of the atmosphere, 
of course, introduces a variable, but that could hardly opcr- 



48 



PRACTICAL CEMENT TESTIXG. 



ate to the extent of 0.04 as given for sample Xo. i. The trend 
of the valves, however, is unmistakable. 

Table A'lIL shows the results of a similar series of tests made 
by the author. The cement in this case was a rotary Portland 
cement from the Lehigh \'alley district, and was exposed to 
the air of the laboratory. These tests also show the same 
tendency although in a lesser degree. 

Another series of tests, taken from the report of the Water- 
town Arsenal for 1901, is given in Table IX. This table also 
shows the effect of drying and igniting. 

Drying a sample of cement at a temperature of 212° Fahr. 
has the eiTect of driving off: the absorbed water while igniting 



TABLE VIII.— Effect of Age on Specific Gravity. 
(Tests by the Author.) 



Age 

Original. . 

1 Month . 

2 Months. 

3 " 

4 " 

6 " . 

9 



Specific 
Gravity 


I 
1 


3-134 
3-125 
3. 121 


I 

I 
2 


3.109 
3 092 
3-073 


2 



039 



Year , 



Specific 
Gravity 



3.006 
3.000 
2.995 



TABLE IX. — Effect of Age on Specific Gravity of Cement. 
(From Watertown Arsenal Report, 1901.) 



-Specific Gravity- 



BRAXD 

A 

B 

C 



Original 

3.12 
3.13 

3-13 



After 
14 days 

3-09 
3.06 

309 



After 
28 days 



J. wo 

304 

3 09 



After 
heatinj 
to 110'' 

3-07 
304 
309 



After 

heating 

.to redness 

316 

315 
3-23 



it with a blast lamp will restore it to the condition of the orig- 
inal clinker. This, however, is not true after a lapse of con- 
siderable time, since the water absorbed gradually attacks the 
cement and breaks it up into hydrated compounds, which when 
dehydrated have a lower density than that of the original ma- 
terial. A certain amount of storage is necessary for any ce- 
ment, during which time the unstable and expansive elements 
absorb water and carbonic acid and thus become inert. A pro- 
longed storage, however, produces the same action on the ce- 
ment itself, until eventually it loses a great part of its hydraulic 
properties. 



SPECIFIC GRAVITY. 



Ar9 



Effect of Composition. — The chemical composition of a cement 
affects its specfiic gravity both directly and indirectly, directly 
in that an excess of the heavier elements such as iron tends to 
increase its specific gravity, while the lighter elements tend to 
lower it, and indirectly in that the necessary degree of burn- 
ing depends upon its composition. The temperature required 
for burning increases as the proportion of lime increases, and 
decreases as the iron and alumina increase. Two cements, 
therefore, may be equally well proportioned and burned and 
be subjected to the same conditions, and yet give very different 
results in the specific gravity, due to the difference in their 
chemical composition. For this reason the test must be con- 

TABLE X. — Effect of Fineness on Specific Gravity of Cement. 
(Tests by the Author.) 



Original Cement, 

Reground once . , 

' ' twice . 



TABLE XI.— The Specific Gravity of Different Sized Particles of the 

Same Cement. 

(From Watertown Arsenal Report, 1901.) 



No. 50 


— Fineness- 
No. 100 


No. 200 


Specific 
Gravity 


1.8 
0.0 
0.0 


12.0 
4.0 
0.0 


27.6 

II-3 
0.6 


3- 

3- 

3 


159 
164 
166 





BBAND 


SPECIFIC GRAVITY 

Size of Grain 
>.0058 .0050 .0034 


(inches) 

.0027 


<.0027 


A... 
B... 
C... 


3.09 

307 
3 08 


3.12 


3.12 
308 


3 12 

3 00 
3 00 


304 
2.0Q 
302 



sidered a comparative and not an absolute one, so that the 
result of every determination must be compared with the nor- 
mal value for that particular brand and not only with regard 
to a certain minimum specification. 

Effect of Fineness. — The fineness of a cement affects the spe- 
cific gravit} in a slight degree, in that the coarse i)a nicies of 
clinker contain a small amount of air which canni.t W- elimin- 
ated by any process. The extent of this effect ma> be seen in 
Table X., which gives the results of tests made bv the author, 
each value being the average of ten determinations. The fine- 
ness of the cement also affects the value in another maimer, 
in that the finer the material the greater will be the absorption 



50 



PRACTICAL CEMENT TESTING. 



of water, hence the specific gravity of the finer particles will 
always be lower than that of rhe coarse. This is illustrated 
in Table XL, taken from the tables in the Report of the Water- 
town Arsenal for 1901. These two conditions tend to neutral- 
ize each other and for routine work need not be considered. 

Effect of Humidity. — The humidity of the atmosphere intro- 
duces a small variable from day to day which must not be over- 
looked, although its amount is practically negligible. This is 
caused by the absorption of water by the cement on damp days, 
and the reverse condition m dry weather. This, of course, can 
be entirely eliminated by drying the samples. For all but the 
finest experimental work, however, this slight variable need 
not be considered. 

In the routine testing of the specific gravity of cement, there- 
fore, the operator has two conditions to investigate — degree 
of burning, and adulteration — -and two variables to consider — 
amount of seasoning, and composition. 

The Weight Test. — The original test to determine the amount 
of burning a cement received was the weight or the apparent 
density test, which consisted in mechanically filling a measure 
with cement, striking it off and determining its weight. This, 
of course, amounts to an extremely crude test of specific 
gravity, in which the measurement of volume is not made on 
the actual particles, but on the space loosely filled by those 
particles. Tht chief source of error in this method lies in the 
fact that the results are dependent so entirely on the uniform 
filling of the measure, the slightest jarring or irregularity in 
the process causing great errors in the results. The values 
also are dependent m a great degree on the fineness of the ma- 
terial, a coarser cement packing much closer, and hence 
weighing more than one which is fine and floury. Hence to 
require a high weight in this test is equivalent to asking for as 
coarse a material as will pass the actual specifications for fine- 
ness. 

Four of the most common forms of apparatus used for this 
purpose are: (i) The double plane apparatus of the French 
Commission on Methods of Testing the Materials of Construc- 
tion (Fig. 20), consisting of two planes at angles of 45°, the 
cement being placed on the end of the short plane, whence it 



SPECIFIC GRAVITY. 



•51 



runs through an opening at the bottom to the second plane 
and thence into the measure. (2) The apparatus designed by 
Prof. Tetmajer (Fig. 21), in which the cement passes through 
an oscillating sieve. (3) Faija's apparatus (Fig. 22), in which 




Fig. 21. — Tetmajer's Apparent Density Apparatus. 



Fig. 20. — Apparent Den- 
sity Apparatus Recom- 
mended by the French 
Commission. 





Fig. 22. — Faija's Apparent 
Density Apparatus. 



Fig. 23. — German Funnel 
Apparatus for Determin- 
ing Apparent Density. 



the cement is i)asse(l llu-ough a screw ctMivovor; and 14) the 
German funnel a])i)at-atus ( iMg. 23). having in the center a rod 
which is rotated to facilitate and e(|ualizo the How of malcnal. 
Several other forms of apparatus are used, but are gener- 
ally similar in ty])e to those shown. This determination is used 



5^ 



PRACTICAL CEMENT TESTING. 



extensively in European laboratories, but has never found favor 
in the United States, and is seldom, if ever, required. 

Forms of Apparatus. — For making tests of the actual specific 
gravity of cement many forms of apparatus have been devised, 
all of which, however, are based upon the principle of meas- 
uring the amoimt of licjuid displaced by a definite weight of 
material. Any liquid can be used provided it has no action on 




E.9 




40 CM. 



-0 




40 CM. 





Fig 24 Fig. 25. Fig. 26. Fig. 27. 

Forms of Apparatus Used for Determinations of Specific Gravity. 

the cement, the most common being benzine, kerosene, tur- 
pentine or paraffine. Care must be taken that, whatever the 
liquid, it be free from water, and also that it be as little volatile 
as possible. 

Mann's Apparatus. — Figure 24 shows the apparatus of Dr. 
Mann, consisting of a small flask which, when filled to a mark 
on its neck, contains a definite amount of the liquid. A burette 



SPECIFIC GRAVITY. 53 

graduated from the bottom and reading to one-tenth of a cubic 
centimeter is filled to a point equal to the volume of the flask. 
A definite quantity of cement is weighed and placed in the 
flask, which is then filled to the neck with liquid from the burette, 
the amount of liquid remaining in the burette after this opera- 
tion being equal to the volume of the cement, x^s shown in 
the figure, the graduations may be so arranged that the read- 
ing can be taken directly. 

The chief objection to this apparatus is the difficulty of re- 
moving the air held by the cement. By shaking the flask when 
a little over half full this error is partially but never wholly 
overcome. Also the shape of the flask, and the necessity for 
frequently handling it make the liquid more than usually sus- 
ceptible both to evaporation and to changes of temperature. 

Mr. Daniel D. Jackson, in the Engineering Record, recently 
described a method and apparatus similar to this in all essential 
particulars, and claimed for it an accuracy exceeding the Le 
Chatelier form. He, however, was compelled always to make 
a correction for temperature. 

Schumann's Apparatus. — The Schumann apparatus (Fig. 25), 
consists of a long graduated tube having a funnel at one end, 
and the other end fitting closely into a flask of al)out 150 c. 0. 
capacity, the tube being graduated from a mark near the l)ot- 
tom up. to 40 c. c, in one-tenth c. c. divisions. The flask and 
tube are filled with the licjuid up to the lower mark on the tube. 
A given quantity of cement, usually 100 grams, is pouroil slow- 
ly through the funnel, the elevation of the li(|uid giving the 
displaced volume. 

This apparatus is open to several objections — the difficulty 
of introducing the cement without its adhering to the siiies 
of the tube, tlie difliculty of eliminating nir bubbles and tlie 
awkwardness of form. 'I^ie cement can l)e prevented from ad- 
hering to the sides of tlie tube by using a l)ng funnel, but 
since as much or even more material will stick to the tnmiel 
than to the tul^e, it is necessary to add enough material to 
elevate the liquid to a definite height, and to determine its 
amount by weighing the .'ipj)aralns before and alter its intro- 
duction. The size of the apparatus, moreover. maUes the 
weighing difficult and awkward. With the exception o\ the 



54 PRACTICAL C EM EXT TESTLXG. 

Le Chatelier, this form of apparatus, in spite of the many ob- 
jections [o it, is probably the most generally used. 

Chandlot's Apparatus. — Chandlot's modification of the Schu- 
mann apparatus is shown in Fig. 26, the modification consist- 
ing in replacing the funnel end of the tube with a closed bulb. 
A mark is placed just below the bulb, so that when the bulb 
is inverted and filled with the liquid the amount contained will 
just equal that of the flask when filled to the lower mark. In 
using this apparatus too grams of cement are placed in the 
fiask, the inverted bulb filled with benzine, and the connection 
carefully made with the tube in a nearly horizontal position. 
The liquid is then allowed to fiow into the flask, the apparatus 
vigorously shaken to remove air bubbles, and the reading taken 
as with the Schumann apparatus. 

The objections to this form are similar to those previously 
given ; the impossibility of entirely removing the air by the 
rough shaking given, and the necessity of handling the ap- 
paratus, introducing probable errors through changes of tem- 
perature. 

Le Chatelier's Apparatus. — Figure 2y shows the specific gravity 
bottle designed by Le Chatelier. The lower bulb with the tube 
above it contains 120 c. c. The bulb half way up the tube con- 
tains exactly 20 c. c, the 120 c. c. mark being placed directly 
under the bulb and the 20 c. c. mark above it. The tube 
above the upper mark is graduated into i-io c. c, starting from 
the upper mark and containing about 4 c. c, thus giving a ca- 
pacity of 24 c. c. from the mark below the bulb to the top of 
the tube. The apparatus is about 30 centimeters in height, and 
the tube about eleven millimeters in diameter. 

Two methods of using this apparatus w^ere originally pro- 
posed : (i) The flask was filled with liquid up to the 120 c. c. 
mark. 64 grams of cement were then weighed out and gradu- 
ally introduced into the end of the tube by means of a funnel 
until the liquid rose to the 20 c. c. mark. The remaining ce- 
ment was then weighed and subtracted from 64, thus giving 
the amount in the flask, which quantity divided by 20 gave the 
specific gravity. (2) The lower part of the flask was filled with 
the liquid as before. 64 grams of cement were then weighed 
and the entire quantity introduced into the tube, making the 



SPECIFIC GRAVITY. cc 

liquid rise into the graduated portion. The reading on the tube 
plus 20 gave the volume displaced by the cement, 64 divided 
by this quantity giving the specific gravity. 

The French Commission on Standard Methods of Testing, 
in proposing this form of apparatus for standard use, recom- 
mended a combination of these two methods, first employing 
method (i) as given, and then introducing into the flask the 
cement remaining after weighing, thus following the second 
method. The result of the test was to be the average of the 
two values thus obtained. 

There are few objections to this form of apparatus, the air 
bubbles being freed from the material in its slow passage down 
the tube, the bulb preventmg the cement from sticking to the 
sides, and there being no necessity for handling it. 

This apparatus is certainly used to a greater extent in the 
United States than any other form, and has been recommended 
by the Cement Committee of the American Society of Civil En- 
gineers, so that it may be considered the standard for making 
this test. 

The Picnometer. — In cases where the specific gravity of ce- 
ment is only determined at infrequent intervals, the picnometer 
or specific gravity bottle is often employed. This consists of 
a small flask usually of 100 c. c. capacity, and provided with 
either a mark on irs stem, or a close fitting glass stopper hav- 
ing a capillary tube in its center. In making determinations 
with this bottle, it is first weighed enipty, and then again when 
filled with benzine. The benzine is then emptied out and a 
weighed quantity of cement introduced, after which the flask 
is filled about two-thirds full with benzine and shaken vigor- 
ously to remove the air bubbles. It is then entirely filled and 
weighed. This weight less that of the cement and of the bottle 
gives the weight of the benzine in the flask, and if this (juantity 
be subtracted from the weight of the benzine necessary to fill 
the flask, it will give the weight of the benzine displaced by the 
cement. Hence if this last weight be divided into that of the 
cement it gives the specific gravity of the cement relative to 
that of benzine, and if this (luantity be then nnilliplied by the 
previously determined specific gravity of th<^ bcn/iiu' it will 



56 



PRACTICAL CEMENT TESTING. 



give the specific gravity of the cement. Expressed in a formula 
this becomes : 

„ „ Cx S 

SP- Gr. - c + B-W 

in which 

C = weight of cement. 
B = weight of bottle filled with benzine. 
W = weight of bottle filled with cement and benzine. 
S = specific gravity of the benzine. 

The specific gravity of the benzine can be found either with 
an ordinary hydrometer or by use of the bottle itself. 
When the bottle is used determinations are made of the weight 
of the bottle empty, when filled with water, and when filled with 
benzine. The specific gravity of the benzine evidently then 
being: 

Sp. Gr. 



H 



where 



b = weight of bottle empty. 

B = weight of bottle filled with benzine. 

H = weight of bottle filled w4th water. 

The specific gravity bottle is open to all the objections of 
presence of air, temperature changes, etc., that have been men- 
tioned in reference to some of the preceding forms. To all 
but the skilled chemist accustomed to handling such apparatus, 
this method is necessarily crude. 

Preliminary Treatment of Sample. — Since the object of this 
test is not only to determine whether the cement is underburned 
or adulterated, but also to find out in a measure the degree 
of seasoning received, it is recommended that the tests in rou- 
tine work be made on the samples in the condition the} are 
received and not on dried or ignited samples, although in 
every case where a cement falls below the specifications a sec- 
ond test should be made on a dried sample to ascertain whether 
an excessive seasoning has caused the low value. 

Also for the reasons given on page 49, it is wrong to use 
cement that has been sifted for these tests, since there is con- 
siderable difference between the specific gravity of the coarse 
and fine particles. 



SPECIFIC GRAVITY. 57 

Sources of Error.— The sources of error that are most Hkely 
to lead to erroneous results, and those most liable to escape 
detection are three: — (i) presence of air, (2) changes in tem- 
perature, (3) evaporation of the liquid. 

The error due to the presence of air bubbles in the liquid can 
only be overcome by the exercise of considerable care. It is 
almost impossible to avoid this error in any form of apparatus 
in which the liquid is poured on the cement, but in those forms 
of apparatus in which the cement is introduced into the liquid, 
the air can be almost entirely eliminated if the operation be 
performed slowly, and if the receptacle be given an occasional 
slight jar to free any bubbles that may have found their way to 
the bottom. 

Changes of temperature probably cause the majority of the 
errors m^ade in specific gravity determinations. The actual 
temperature at v/hich the test is made does not affect the re- 
sults, but any change in that temperature at once introduces 
errors. For this reason the different forms of apparatus arc 
often immersed in water before the initial and final readings 
are taken for a sufficient time to acquire the. temperature of 
the water. This proceeding, however, requires considerable 
time, and is not necessary if care be taken that the room in 
which the tests are made is kept free from draughts of cither 
hot or cold air, and that no other condition exists which is like- 
ly to cause changes in the temperature. Care especially nnist 
be taken never to touch the apparatus with the fingers, since 
their heat will appreciably affect the reading in a very short 
time. 

The error due to evaporation is never great in the or(Hnary 
forms of apparatus if only a reasonable amount of time l)c em- 
ployed in making the test. At ordinary temperatures, and 
where the entire determination can be completed in about five 
minutes, the evaporation may be entirely neglected. It should, 
however, be considered where a much longer time is retjuirod. 
In placing the apparatus in water to make the temperature 
correction, the top should always l)e tightly corkeil. since other- 
wise the error caused by evaporation may actually exceed the 
error that the operator is endeavoring to eliminate. r>oth the 
errors of temperature and evaporation can be detected by the 
use of a second fiask, used as a 1)lank. in which no cement is 



58 



PRACTICAL CEMEXT TESTIXG. 



pur, but which is subjec:ed :o the same conditions as the first, 
and on which readings are made before and after :he experi- 
ment, the difference being the correction to be apphed. 

Another precaurion that should ahvays be employed is, after 
filling a llask, to allow a short time before taking the reading 
so as to permit the hquid on the sides of the tube to run down, 
this often making a considerable difference in the results. 

The Author's Method. — The following method is used by the 
author in the Philadelphia Laboratories for making determina- 
tions of specific gravity : 

All the samples which are to be rested, the appararus, and 




Fig. 2S. — Apparatus Used by the Author tor Making Deienninations of Srecinc 

Gravity. 

the benzine are first allowed ro stand in the room in which the 
tests are to be made for ar least an hour in order that they 
all may acquire a uniform temperature, care being taken that 
the doors and windows are so arranged that there can be no 
draughts nor currents of air. Two Le Chatelier specific gravity 
bottles, which have been carefully calibrared, are used alter- 
nately in making the determinations, and benzine, which has 
been determined to be neither very volatile nor hygroscopic, 
is emplo} ed for rhe liquid. Sixty-four grams of cement are 
weighed, on a piece of paper, in a beam balance of 5 milligrams 
sensibility (see Fig. 28). The flasks are filled with benzine a 



SPECIFIC GRAVITY. ^g 

little above the lower mark, allowed to stand half a minute, and 
then- adjusted carefully to the mark by means of a glass tube 
used as a pipette. A funnel, four inches in diameter, having a tube 
of such a width that it will just enter the top of the apparatus, 
is placed in the ring of a retort stand at such a height that 
the bottom of the funnel reaches about half an inch below the 
top of the flask, and also so that the apparatus is free to be 
moved up and down slightly without disturbing the funnel. 
The entire sixty-four grams of cement are poured into the fun- 
nel, the last traces of material being removed from the paper 
by means of a camel's hair brush. 

The cement is then gradually forcea through the funnel with 
a narrow glass rod, and at the same time the flask is given a 
jarring motion by raising it about a sixteenth of an inch and 
dropping it, holding it at the top of the tube where the tempera- 
ture of the fingers will not affect the benzine. Working on a 
wooden table, and exercising reasonable care, there is no dan- 
ger of breaking the apparatus, but if it is desired to further in- 
sure its safety, a piece of blotting paper may be placed under it. 
This jarring serves the double purpose of preventing the cement 
from clogging in the upper bulb, and also of freeing it from 
particles of air. 

When all the cement has been introduced, the last traces 
are removed from the funnel and rod with the camel's hair 
brush, and the funnel removed. If any cement is clinging to 
the sides of the apparatus, it is pushed down with the glass rod, 
which is in turn scraped against the edge of the tube to re- 
move the last traces of benzine. 

After allowing the flask to stand half a minute, the reading 
is taken, interpolating to i-ioo c. c. A mark is placed on a 
far wall at the same height as the upper mark of the apparatus, 
so that by sighting on this mark, parallax is avoided. By 
means of a table similar to Table XII., the specific gravity is 
at once obtained and entered on the record. Since great care is 
exercised to prevent changes in temperature the flasks are not 
immersed in water during the operation. 

The flasks are cleaned by inverting and shaking tliem over 
a precipitating jar about five inches in diameter, partially filling 
again and shaking until clean. The benzine is scparateil by 



6o 



PRACTICAL CEMENT TESTING. 



TABLE XII. — Values of Specific Gravity in Terms of the Readings of the 
Le Chatelier Apparatus, When Using 64 Grams of Cement. 





0.00 


O.OI 


0.02 


0.03 


0.04 


0.05 


0.06 


0.07 


0.08 


0.09 


20.00 


3.200 


3.198 


3-197 


3-195 


3-194 


3.192 


3.190 


3-188 


3-187 


3.186 


.10 


3-184 


3.182 


3-181 


3-179 


3-178 


3.176 


3-174 


3-173 


3-171 


3-170 


.20 


3.168 


3.167 


3-165 


3-164 


3.162 


3 161 


3-159 


3-158 


3-156 


3-155 


•30 


3-153 


3-151 


3-150 


3-148 


3-147 


3-145 


3-143 


3-142 


3-140 


3-139 


.40 


3-137 


3136 


3-134 


3-133 


3-131 


3-130 


3.128 


3.127 


3-125 


3-124 


•50 


3.122 


3. 121 


3-119 


3. 118 


3. 116 


3-1^5 


3-113 


3. 112 


3. no 


3.109 


.60 


3.107 


3.106 


3-104 


3 103 


3.101 


3.100 


3098 


3-097 


3.095 


3-094 


• 70 


3.092 


3091 


3.089 


3.088 


3.086 


3-085 


3-083 


3-082 


3.080 


3-079 


.80 


3-077 


3076 


3-074 


3-073 


3.071 


3.070 


3.068 


3.067 


3.065 


3-064 


.90 


3.062 


3.061 


3-059 


3.058 


3-056 


3-055 


3-054 


3.052 


3051 


3-049 


21.00 


3.048 


3-047 


3-045 


3 -044 


3.042 


3-041 


3 039 


3-038 


3-036 


3-035 


.10 


3-033 


3032 


3-030 


3.029 


3.027 


3.026 


3-025 


3-023 


3.022 


3.020 


.20 


3.019 


3.018 


3.016 


3-015 


3-013 


3.012 


3. on 


3.009 


3.008 


3.006 


•30 


3-005 


3.004 


3.002 


3.001 


3.000 


2.999 


2.997 


2.996 


2-995 


2.993 


.40 


2.992 


2.991 


2.989 


2.988 


2.986 


2.985 


2.983 


2.982 


2.980 


2.979 


•50 


2.977 


2.976 


2.974 


2.973 


2.971 


2.970 


2.969 


2.967 


2.966 


2.964 


.60 


2.963 


2.962 


2.960 


2.959 


2.957 


2.956 


2.955 


2-953 


2:952 


2.950 


.70 


2.949 


2.948 


2.946 


2.945 


2.944 


2-943 


2.942 


2.940 


2.939 


2-937 


.80 


2.936 


2-935 


2-933 


2.932 


2.930 


2.929 


2.928 


2.926 


2.925 


2.923 


.90 


2.922 


2.921 


2 919 


2.918 


2.917 


2.916 


2.914 


2.913 


2.912 


2.910 


22.00 


2.909 


2.908 


2.906 


2.905 


2.904 


2.903 


2.902 


2.900 


2.899 


2.897 


.10 


2.896 


2.895 


2.893 


2.892 


2.891 


2.890 


2.888 


2.887 


2.886 


2.884 


.20 


2.883 


2.882 


2.880 


2.879 


2.878 


2877 


2.875 


2.874 


2-873 


2.871 


•30 


2.870 


2.869 


2.867 


2.866 


2.865 


2.864 


2.862 


2.861 


2.860 


2.858 


.40 


2.857 


2.856 


2.854 


2.853 


2.852 


2.851 


2.849 


2.848 


2.847 


2.845 


•50 


2.844 


2.843 


2.842 


2.841 


2.839 


2.838 


2.837 


2.836 


2-834 


2.833 


.60 


2.832 


2.830 


2.829 


2.828 


2.827 


2.826 


2.824 


2.823 


2.822 


2.821 


.70 


2.819 


2.818 


2.817 


2.815 


2.814 


2.813 


2.812 


2. 811 


2.809 


2.808 


.80 


2.807 


2.806 


2.805 


2 804 


2.803 


2.802 


2.800 


2-799 


2.798 


2.796 


.90 


2-795 


2.794 


2-793 


2.791 


2.790 


2.789 


2.788 


2.787 


2.785 


2-784 


23.00 


2.783 


2.782 


2.781 


2.779 


2.778 


2.777 


2.776 


2-775 


2.773 


2.772 


.10 


2.771 


2.770 


2.768 


2.767 


2.766 


2.765 


2.763 


2. 762 


2.761 


2.759 


.20 


3-758 


2-757 


2.756 


2-755 


2.754 


2-753 


2.751 


2.750 


2.749 


2.748 


" -30 


2 747 


2.746 


2-745 


2.743 


2.742 


2,741 


2.740 


2.739 


2.737 


2.736 


.40 


2-735 


2-734 


2-733 


2.731 


2.730 


2.729 


2.728 


2.727 


2.725 


2.724 


•50 


2 723 


2.722 


2.721 


2.720 


2.719 


2.718 


2.716 


2.715 


2.714 


2.713 


.60 


2.712 


2. 711 


2 710 


2.709 


2.708 


2.707 


2.705 


2.704 


2.703 


2.702 


.70 


2.701 


2.700 


2.699 


2.698 


2.697 


2.696 


2.694 


2.693 


2.692 


2.691 


.80 


2.690 


2.689 


2.688 


2.686 


2.685 


2.684 


2.683 


2.682 


2.680 


2.679 


.90 


2.678 


2.677 


2.676 


2.675 


2.674 


2.673 


2.671 


2.670 


2.669 


2.668 


24.00 


2.667 


2.666 


2.665 


2 664 


2.663 


2.662 


2.660 


2.659 


2.658 


2.657 



SPECIFIC GRAVITY. 6l 

filtering, so that it can be used repeatedly, one gallon sufficing 
for about lOO determinations. 

Two men make these tests, one weighing the cement and 
cleaning the flasks, and the other operating the flask and tak- 
ing the readings. Experienced men following this method can 
easily make from lo to 12 determinations in an hour. Two 
men in the Philadelphia Laboratories once made 54 tests in 
four hours, and some of these tests being repeated for curiosity 
it was found that in no case did the error exceed 0.006. 

Whenever a test falls much below the average value for that 
brand of cement, or whenever it falls below specifications (3.100) 
a check test is made, and also a test made on a dried sample, 
all 01 which are entered in the records. 

Determinations made by experienced men following this 
method can be considered accurate to the second decimal. 
The following are the results of ten tests on the same sample 
of cement made under the author's direction : These samples 
were mixed in with the regular tests of the day, and the oper- 
ators had no knowledge that any special tests were being made, 
and hence exercised no unusual precautions. The results were: 

3-143. 3-139. 3-141, 3-138, 3-138, 3-137. 3-136, 3-140, 3-143. 3-137; 
average, 3.1392; total range, 0.007; average departure from 
mean, 0.002; probable error of one result, 0.0017. It is thus 
evident that the statement that this method is accurate to the 
second decimal is well within the bounds of probability. 

Interpretation of Results. — With the exception of the test for 
soundness, there is probably no test in which incorrect or mis- 
leading inferences can be drawn so readily as in that of spe- 
cific gravity. This is chiefly due to the fact that the test is 
comparative rather than absolute. For example, one cement 
may average a specific gravity of 3.16 and another 3.11. Now, 
a sample of the first testing 3.12 might be underburned ov con- 
siderably adulterated, and yet be higher than a lu^rnial vahic of 
the second brand. For this reason an (~)perator must have con- 
siderable experience with average values before he can aeeu- 
rately interpret the result of a single test. .Vgain. an abiu»nnally 
low value may be the result of excessive seast^ning. Now. if 
this seasoning lias not been sutlicienl lo lower the sh-ength bo- 
low requirements, the cement is undoubteiHy in lar belter con- 
dition for service than if it were fresh, because il will almost 



62 PRACTICAL CEMEXT TESTIXG. 

certainly be volume constant. The greatest difficulty that many 
consumers experience is in the securing of well seasoned ma- 
terial, and yet testers of cement frequently reject such material 
merely because its specific gravity is low, thus defeating their 
own ends. 

A sample of cem.ent that tests below the average in specific 
gravity should be examined for adulterations and should also 
have tests made on dried and ignited samples, but if it is shown 
to be free from adulterations, sufficiently strong, and sound, it 
should never be rejected merely because its specific gravity may 
be somewhat below requirements. 

The specific gravity clause, however, should be a feature of 
every specification, in order that a cement proven to be under- 
burned or adulterated may be rejected on its strength, even 
though it may pass the other tests. 



Mi 



CHAPTER VIL 

FINENESS. 

Although the fineness to which a cement is ground may be 
of little consequence in itself, yet its effects on the other prop- 
erties are so far reaching that the test becomes one of consid- 
erable importance. It is interesting to note how this condi- 
tion has gradually become realized wdth the growth of the in- 
dustry. In the old days of testing many of the records show 
cements leaving residues of as much as 25 or 30 per cent, on 
a No. 50 sieve, while a test leaving that much residue on a No. 
200 sieve is now considered poor, some of the modern cemencs 
leaving a residue of even less than 15% on this sieve. 

It has been definitely proven that, at least in the early stages 
of the hardening of cement, only the ver} fine particles are ac- 
tively hydraulic. The fineness of the material, therefore, is a 
measure of its cementing value, and a fine cement, accordingly, 
will be much the stronger when mixed in a mortar, or it can 
be mixed with a larger proportion of sand than a coarse one 
and yet attain the same strength. For reasons explained later, 
however, a neat cement mixture is usually less strong when 
made of fine material, although this is comparatively unimi)or- 
tant on account of the infrecjuency of the use of neat mixtures 
in practice. 

Also, since the hardening of cement is caused b\- the sohi- 
tion and subsequent crystallization of certain of its elements, 
it is evident that this action will be (juickened by the fineness 
of the particles, hence the finer the grinchng, the sooner will 
the ultimate strength be attained. Another eft'eet oi st^me- 
what doubtful advantage is that the finer cement will be (juieker 
setting, the same reasons given for early hardening api^lving \o 
the setting with ecjual force. 

Most important of all, however, is the fact that wiili tiiuT 
grinding, the liability to unsoundness becomes less, since the 
small particles become seasoned more (|uiekl\ and the expan- 
sive elements thus become inert. 

Detailed discussions of the effect of fineness on time of set- 



64 PRACTICAL CEMENT TESTING. 

ting, strength and soundness will be found in the chapters de- 
voted to those subjects, but sufficient is here stated to show 
the reasons for and the importance of making this test. 

Methods of Determining Fineness. — Fineness is customarily 
determined by sifting through a series of sieves of different 
mesh. Many other devices have been proposed, most of them 
attempting separation by currents of air or of a liquid, but 
none has yet proved sufficiently accurate and at the same time 
simple and quick enough to replace sifting in routine work. 
Separation by some such method is much to be desired, how- 
ever, for the reason that even the finest sieve now in use is not 
capable of determining the size of the smallest, and hence the 
most active particles, and moreover, the amount of material 
passing the finest sieve does not necessarily give a measure 
of the amount of flour present. 

"Dr. W. Michaelis,* the great German specialist, recom- 



TABLE XIII. 


— Gradation of Fineness Recommended by Michaelis for 






Cement Testing. 






(From Johnson's "Materials of Construction.) 


Number of Meshes per 

Square Square 
Centimeter Inch 


^Diameter of Wire-^ 

In In 
Millimeters Inches 


^Width of 
In 

Millimeters 


Mesh-> 

In 
Inches 


/ Area of Mesh s 

In Square In Square 
Millimeters Inches 


900 4, 200 


0.133 


00052 


0.20 


0.0080 


0.04 00000610 


3,600 23,500 


0.067 


0.0026 


0. 10 


0.0040 


0.01 0.0000150 


15,000 97,000 
60,000 390,000 


0.033 
0.002 


0.0013 
00008 


0.05 
0.02 


0020 
0.0008 


0.0025 0000040 
0004 0. 0000006 



mendsf that two sieves be used, No. 75 and No. 150 (30 and 60 
meshes per cm.) and in addition to these the Schone washing 
apparatus with rates of upward flow of the alcohol of 2.8 inches 
per minute, giving particles of cement which would pass a No. 
300 sieve (120 per centimeter), and also of i inch per minute 
upward velocity, giving particles which would correspond to 
those passing a No. 600 sieve (240 meshes per centimeter). 
This washing process added to the use of the two sieves would 
enable one to graduate the cement as in Table XIII. 

'The relation between the largest diameter of particle and 
the rate of upward flow for absolute alcohol and Portland ce- 
ment he finds to be 

d ^ 0.036 V ^/" 

where d =^ largest diameter in millimeters, and v = upward 

♦From Johnson's "Materials of Conetruction," pp. 412-413. 
f'Thonindugtrie-Zeitung," Aug. 24 and Nov. 23. 1895. 



FINENESS. 65 

velocity of flow in millimeters per second in the c}iindrical part 
of the washing apparatus." 

"As a result of this further analysis for fineness, it appears 
that the conclusions drawn from an analysis with the Xo. 75 
and the No. 175 sieves (30 and 70 per centimeter) may be en- 

TABLE XIV. — Comparative Analyses of Two CGments. 
(From Johnson's "Materials of Construction.") 

S.ample No. 1 « ^Sample No. 20-^ 

Sieve-Gauges (Meshes per Linear Inch) Par-t^ Total Poi-tc Total 

Where Diameter of Wire = Width of Mesh -fares Passing -t^arts Passing 

Per Cent Per Cent. Per Cent. Per Cent 

Ketained on No. 75 Sieve 

Passed No. 75 and Retained on No. 175 Sieve 
" 175 " " " " 300 " 
" " 300 " " " " 600 " 
" " 600 Sieve 



65 


99-35 


I 55 


98.45 


7-75 


91.60 


740 


9105 


42.98 


48 62 


19- 74 


71-31 


17 75 


3087 


25 27 


4604 


3o«7 




46.04 





100.00 



tirely erroneous. Thus among the many analyses given by 
Michaelis in these articles are the two analyses in Table XIV. 
of cement ground in the same manner, on French buhrstones, 
5 feet i.i diameter." 

"The total percentage passing the No. 175 sieve was 91.60 
for sample No. i, and 91.05 for sample No. 2. This would ap- 
pear to give No. I a slight advantage. There was stopped at 
the next stage, however, 43 per cent, of No. i and only 20 per 
cent, of No. 2, thus leaving only 48.62 per cent, of No. i to pass 
the 300 sieve, while of No. 2 there passed 71.31 per cent. Innal- 
1} there was but 31 per cent, of No. i to pass the washing test 
which corresponded to a No. 600 sieve, while 46 per cent, of 
No. 2 passed this last test of fineness. It thus ai^pears that 
sample No. 2 is much finer ground than No. i, ahhinigli this 
would not appear from the most severe sieve-tost it is possible 
to make, it being impractica1)le to use any finer sieve than 
about 175 meshes per linear inch (70 per centimeterV" 

"Dr. Michaelis strongly urges, therefore, that in all .-scien- 
tific and expert investigations of fineness the washing tests be 
eni])loye(l." 

Figure 29 shows a common form of washing apparatus for 
separating a powder into different sized particles. A lii|uid 
under a constant head flows into tlie small tube, rises into the 
large tube, and overflows at the side. Rcfore the flow of the 



66 



PRACTICAL CEMENT TESTING. 



liquid commences the powder is inserted into the large tube 
and vigorously stirred so that it is all in suspension, then, when 
the liquid begins to rise in the tube, the smaller particles are 

carried off, while the larger remain 
in suspension or collect at the 
bottom, from whence they can be 
drawn off through the stop-cock, 
collected, and the percentage deter- 
mined. The size of the particles 
carried off, depends, of course, on 
the velocity of the liquid, which is 
regulated by adjusting the height 
of the reservoir. 

Another method sometimes em- 
ployed for crude washing tests of 
fineness consists in placing a 
definite amount of material in a 
beaker, filling it with w^ater, stir- 
ring it, allowing it to settle for a 
few^ seconds, and then pouring off 
the water carrying the flour in sus- 
pension, repeating the process until 
the water is practically clear, dry- 
ing the residue, and determining 
its amount. For rough tests, this 
method may be occasionally used, 
but for regular work it is crude and inaccurate. 

In routine testing, therefore, recourse is made to sifting, not 
so much on account of any intrinsic merit in the method, but 
because no other scheme has been devised which is both ade- 
quate and practicable. 

Sieves. — The sieves commonly found on the market for use 
in cement testing are the No. 50, No. 100 and No. 200. Sieves 
intermediate between these, especially the No. 74, No. 120 and 
No. 175 have been, and even still are occasionally employed, 
but scarcely to an extent to warrant consideration. Of these 
different sieves, the No. 200 is by far the most important, 
since only that part of the cement passing this sieve is truly 
active, at least in the early stages of its hardening. More- 
over, it is not true, as many imagine, that any definite ratio ex- 




FiG. 29. — Apparatus for 
Determining Fineness by 
Washing. 



FINENESS. 



67 



ists between the residues on the Xo. too and No. 200 sleves, 
This is clearly shown m Table XV. The series of tests in this 
table are taken from regular routine determinations made in 
the Philadelphia Laboratories and show that the amount of 
residue on the No. 100 gives scarcely any indication of what 
will remain on the No. 200. It is, therefore, evident that the 
use of the No. 200 sieve is essential if the effective fineness of 
the cement is to be determined. 

The employment of the X"o. 100 sieve is desirable since it 
shows the gradation of the material, and also since It marks 
in a measure the amount of material capable of possessing any 
cementing properties. Cement particles passing the X^o. 100 

TABLE XV. — Showing Lack of Proportionality Between Residues on No. 100 

and No. 200 Sieves. 

(Tests by the Author.) 

No. / Fineness — * Ratio of 

No. 50 No. 100 No. 200 No. 200 to No. 10. 

I o.o 48 21 9 4.6 

2 01 82 17.7 2.2 

3 00 64 25.3 4 O 

4 0.0 2.1 180 8.6 

5 0.2 10.4 250 2.4 

6 01 6.3 192 3.0 

7 0.0 14.7 27.3 1.9 

8 0.5 58 19.2 3.3 

9 00 3.6 18.0 5.0 

10 0.0 9.2 24.1 2.6 



sieve always possess some activity, but those remaining on this 
sieve may, for all practical purposes, be considered inert. 

The No. 50 sieve gives little additional information, but as 
the results are often interesting in showing the character of 
the clinker, and sometimes in detecting adulterants, and since 
the test requires but an insignificant amount of time, when 
made in connection with the other siftings, its use is comiKira- 
tively general. 

The intermediate sieves give httle or no additional informa- 
tion, and hence are not recommended. 

Wire Cloth. — Probably the greatest dif^culty in the wav of 
the standardization of the fineness test is encountered in ihe 
procuring of uniform wire cloih. At present, the grreatost 
variation will be found even among the so-called standard 
sieves. No. 50 and No. 100 sieves of comparative accuracy' 



68 



PRACTICAL CLMEXT TESTIXG. 




can hi^ procured, l^ut even tlie best Xo. 200 
sieves rarely count over 194. The author 
has seen, in laboratories of considerable 
reputation, No. 100 sieves counting- as low 
as 78 X 84;, while No. 200 sieves counting^ 
but 150 are by no means uncommon. Evi- 
dently, many of the seeming- discrepancies 

Fig. 30.— Linen Tester's in the results obtained by different labora- 

Microscope. tories can be traced to this source alone. 

Standardization of wire cloth can probably be reached best 

by stipulating definite limits by actual count of the number 



.....aa.aa.;:.;;^;^:;.. . . 


.aaaaaaaaaaaaaaiBiaBaaaaaaaaiaaai . 


<a«aBBBBaBBtaBia»ai>BaaaBBBBaB«aaar *. 


^ ■BaaaBra'aBaaaaaaaaa-iaBBaaaBBaBaaiaaaaaaaa 


^aaaaaaaaaaaaaaaaaaaaiaaaaaaaBaaaiaaakaBaah 

.aaapaaaaaaaaaaaaaaaaaiaaaaaaaaaaaiBaaBaamaa^ 

oaBaaaaBBBaaaa aaaaiaaaa ■aaaaaaaaaaiaaaaaaaaaa 

•"■aaaaaaaaaaaB^BaaaaBai ■aaaaaaaaaaiBaaBaaaaaafe 
.abBB'iiaaBaaaaaaaaaaBBaa^>aB>Z>ZZ_ZZ._ — 7- 


aBaaaaBaaaaaBaaaaaaaBflBaBaaaaaaaaaaiaBaaaBaaaaBi 


aaaaaaaaaaaaaaaaBBaaaataiaaaaaiaaaaaiattsaaaaaaa^a 

■■aaaBaaaBaaaaaaaaaaacaMaaaaBaaaaBaaaaaiaaaaaaaB^' 
.aBBaaaaaaaaaaaBaaaaaaBaaRaaaaaaaaaaBiBBaaaBiBaaaBac 
aaaBasaaaaBBaaaBaBBaaaaaiaaaaaaBBaaaaaaa^aaaBaBaBa 
aBaaanaBaBBaaBBaBBBaiBiaiiaaaflaBBBaiBBaBaaaBaaBaa 


■ BiBiiiaiaiBaaiaaaaiiBiaiiiBBaiaaBBBiBBaaaBiliaBaaa 
aBaaaaBaBBBaaBBBBaati'iaiaiaaaaaiaaBBaiBBaaaaaaaaaaa 
BBaaaaaBaBaaaaBBaaae.tBiBiaiaaiiaaaBBiBBaaBBaaaaBaa 

■■■■■■■aaaaaaaaaaBaa«a««aaBaaaBaaaBaaaaa«aB«aMaaa» 


aaaaBapaiaaaaiaiaiaaiaiHiiiiiiiiiaaiaiaiiaaijiMaaB 

■■■■aaaB' aaaBBBaBaaa a a bm aaaaaia aaaBBaaaaa aaa a a aZ 


■ Biiiiiaa ■■■laBaaBiiaiaiiaaaaaaBBaBaaaa* aaB-aaaB* 
BasBBBaaaBBBBBaaaaaaaaaaiaaaBaaaBBaaaaBaaBaaaBaa as 
BBaaBaBaaaaaaBaaaB^iiBtBiaiaBaaaBaBBaaaiBBBaaBBBB 

BaaaBaaBaBaaaaaaaa2aaaaaaaaa.aa«aaaa*.a._.H:Zr:".r 


aBaaaaBaBaaaaBBBaBBaiBiaaiaiBBiaaaBBiaaBaaaBaaaaaA 
aaaaa8BBaa8BBaBBBaiiB<Biai*BaaaiaaaBaaBBaaBiSi""Za. 
BBBaBaBBaaaBaBBaBBBaiBiatBBaaiaaiflaaaaaiBaBBaaaaa 


■ aaiaiaaiBiaiiaiaaaaiaaa ■Baa*aaaBiii'";S"::,:;? 
!:!!;!■•■;■■■■■■■■■"»■**«•••■■■■■■■■•■■••■■»«•*»> 


<««aafaaaBR«aaBBaaBa«Bp««««B«aaaB«aBpa«aaBaBaa«>' 


<iaaaBta'a*aaa.aaaafBf«««,ai:;;;«;"S:^S*Z!"* 

'!!!!"•'"••""•■•■■'•••■»•""■■•«■■••••••••••'> 

• B«Ba«a»Baa*aaa«B<ai«taaaa««a«aa*iaBiaaBii 
*«^««faiit«aiaiatf«f«tajaa««a •••*«-(««««» 

'•••»•• a ••a«a«»aa«a»»"«»^«»»aB««««i«i» 

■••■•••B»»a«a»««saBia «.»««•»•••. «,-„i.i 
•> « > . * a a • > • a • • a » « t • a « a . V < « I a a 1 • • 



Fig. 31. — Illustration of Defective Wire Cloth. 

of meshes per inch. Two otlier methods, often adopted, are 
testing by comparison with a standard, and finding the diame- 
ter of the largest particles passing the cloth. The first of these 
methods, however, has the objection of removing a basis of 
comparison between different laboratories, while the second is 
rather too difficult for the average cement tester.=^ The sim- 
plest method of counting wire cloth is by the use of an ordinary 

*For a degcription of this method see article by Allen Hazen in the report of 
the >Ta9sachusett9 State Board of Health for 1892. 



FINENESS. . 5q 

linen tester's microscope (see Fig. 30), wliich can be procured 
at an nisignificant cost, is sufficiently accurate, and furnishes 
a method of standardization that can be readily employed even 
by the poorest equipped of field laboratories. Of course, it is 
evident that a piece of wire cloth might count exactly the 
proper number, and yet be far from accurate. This is well 
shown in the photographs* in Figs. 31 and 32. Both of these 



Fig, 32 —Illustration of Detective Wire Cloth. 

sieves show irregularity in spacing, uhile llu- fnuT sicxo also 
shows distortion of mesh probably caused in luoiinting. Dis- 
torted sieves or those as badly spaced as that in (igin-e 31. 
should never be used, but if the only irregularity consists of 
one wide space it may, if desired, be si(^pi)ed with solder. 

In regard to the diameter of the wire from wliicli ilie sieves 
are made there is comparative unifornu'l\'. ne.nK all the niak 
ers using the following sizes: — for No, 50. ^^^ ( >. I'-, gauge. 

♦Photographs lonned l)y lloiiry S. Sptu-Uman KriKlnerrliiK Co.. I'liilii.. Pi 



JO PRACTICAL CEMEXT TESTING. 

for No. 100, 40 O. E. gauge, and for No. 200, 42^ B. and S. 
gauge. It has frequently been urged that, in order to obtain 
better uniformity, the wire in all sieves be made one-half the 
width of the opening. This suggestion, however, is scarcely 
practicable, since none of the standard gauges in the market 
conforms to the diameter necessary to meet this requirement. 
Moreover, the wire for the No. 200 sieve w^ould be only 0.0017 
inches in diameter, which would be difficult, if not impossible, 
to procure, and w^ould at best make an extremely flimsy and 
easily broken sieve. The expense and difficulty of procuring 
this wire, therefore, would scarcely be w^arranted for the sole 
purpose of obtaining a uniform ratio betw-een the width of the 
wire and the opening. 

The following specifications^'^ have been used by the author 
for the past four years, in purchasing wire cloth for use in the 
Philadelphia Laboratories, and have been proven satisfactory : 

1. Cloth for cem.ent sieves to be of brass wire of the follow- 
ing diameters : 

No. 50, No. 35 O. E. gauge, 0.0090 inches. 
No. 100, No. 40 O. E. gauge, 0.0045 inches. 
No. 200, No. 42 J B. and S. gauge, 0.00235 inches. 

2. Mesh to counl as follows : 

No. 50, not less than 48, nor more than 50 per linear inch. 
No. 100, not less than 96, nor more than 100 per linear inch. 
No. 200, not less than 188, nor more than 200 per linear inch. 

3. Cloth for No. 50 and No. 100 sieves to be woven ; cloth 
for No. 200 sieve to be twilled.^ 

4. yiesh to be square and to show no great irregularities of 
spacing. 

Mechanical Sifting. — For the mechanical operation of sieves, 
a great number of devices, more or less ingenious and efficient, 
have been designed. Figure 33 shows a sifting machine for- 
merly used in the Philadelphia Laboratories. This was de- 
scribed by Mr. R. L. Humphreyi as follows: 'Tt is operated 

♦These specifications have recently been adopted by the Committee of the 
American Society of Civil Engineers on Uniform Tests of Cement. See Appendix A. 

tWoven wire overlaps every alternate strand— tvv^illed wire laps the strands in 
pairs. Woven cloth of 20O meshes cannot be pro cured in the market. 

|In a paper entitled "A Few Remarks on the Testing Laboratory of the City of 
Philadelphia," read before the Engineers' Club of Philadelphia, April 1, 1899. 



FINENESS. 



71 



by a small electric motor, and consists of a wooden frame (i 
ft. ID ins. long, 14 ins. wide and 10 ins. deep), supported by 
four legs ; a box 14 ins. long, 10 ins. wide and deep, fits close- 
ly into the frame. This box has trunnions in the center of two 
sides which move in grooves in the outside frame ; and is moved 
to and fro by a crank connected to a crank-disk having a throw 
of ij ins. The box holds four sets of brass sieves, each set 




^^^^^^^^^^^^^^^^^^^ 



Fig. 33. — Mechanical Sifting Machine Used in thr 
Philadelphia Testing Laboratories. 

consisting of a No. 100 and a N(^. 200 sieve, a cover, and a jian. 
all nesting into each other. These siexcs an- held in place 1)\ 
means of two clam])s. 11ie driving pulley makes 100 revolutions 
per minute, and the ]k»\ hi)l(;ing the sieves makes Jcx) move 
menls ])er minute to and fro. 'I'he sie\ing frame has a tilling 
motion, and the rapi(ht\ of the nioiion imparts to it a jerking 
movemenl." 



72 



PRACTICAL CEMENT TESTING. 




Fig. 34.— The RiehleHand Sand 
Sifter. 



The Riehle hand sand sifter (Fig. 34), as its name implies,. 
was designed for the sifting of sand, but may also be used for 
cement. The frame holding the sieves is fastened to an upright 

revolving crank at one end, while 
the other end is held in a slot in 
the upright. The turning of the 
hand wheel gives to the sieves a 
circular motion and also a jar at 
the point where the crank passes 
its dead center. 

A simple device for cement sift- 
ing is shown in Fig. 35. This ap- 
paratus was designed and is used 
by Mr. S. S. Voorhees, and its. 
operation is self-explanatory. An 
ordinary fan motor furnishes the 
power, driving the frame through a 
crank wheel having a throw of 2 
ins. The holes to receive the sieves 
are about half an inch larger than the sieves themselves, which 
are strapped in loosely to allow some play. A rubber mat is 
used to break the pound on the bottom of the sieve. The mo- 
tion given to the sieves is the same as that of the machine in 
Fig. 34, except that in this case the throw is vertical, while the 
other is horizontal. 

These three machines can be considered as types of the best 
of the many sifting devices in use, although the actual num- 
ber of different forms nearly equals the number of testing' 
laboratories. 

Appliances for the mechanical sifting of cement are employed 
either for the purpose of securing greater uniformity and accu- 
racy, or to economize time and labor. It has been the author's 
experience, however, that neither of these results is accom- 
plished for the following reasons : In machine sifting one of 
two methods must be followed, (i) the machine is given a defi- 
nite number of turns or shakes and the amount passing or re- 
tained on the sieves weighed directly, or (2) the sifting is con- 
tinued until a definite amount of material ceases to pass the 
sieves at the end of a definite number of turns or shakes. 
The first of these methods is manifestlv unfair and inaccu- 



FINENESS. 



73 



rate, because of the different speeds with which cements will 
sift under different conditions, those most affecting it being the 
age and specific gravity of the material, and the dampness of 
the material and of the atmosphere, conditions with which all 
practical operators are thoroughly familiar, but which are often 
overlooked by those directing the work. As an example of 
the effect of age on the speed of sifting, the author tested a 
fresh cement on a mechanical sifter and obtained a certain 
result at the end of thirteen minutes ; four months later, it was 
again sifted under preciseh similar conditions, and reached 




Fig. 35.— a Simple Design for a Mechanical Sifter. 

the same result in seven and a half minutes, and ai ilii 
of thirteen minutes showed a fineness 2.4% groalcr than 
previously ol)tained. The effect of the other conditions is 
vious. Other things being equal the heavier cenKMit will 
faster than the lighter one, while excessive dampness will 
to retard it. Two cements, therefore, of actually the same 
ness may give widely variant results if tested in this manner 
The second of these methods is more accurate, bnt tin 
tcndant disadvantages are: I'irsl, (liat it inlro(inces the 
sonal e(|uation, to eliminate wliieli so nuieh troubU' Iia^ 1 



nul 
iha: 
ol)- 
si.'t 
I (.'11(1 
tine- 



piT 

>een 



74 PRACTICAL CEMEXT TESTLXG. 

taken, because the exact point of completion is left more or less 
to the discretion of the operator, and, second, that it actually 
takes more time to sift in this manner, where the sieves must 
be fitted together and put into the machine several times for 
each determination, than in the method of hand sifting, where 
the point of completion is more easily observed. 

To the arguments against mechanical sifting must be added 
the cost of installing another piece of apparatus, and the slight 
likelihood of this method being adopted by the smaller labora- 
tories, thus making comparisons of results difficult. Although 
devices for machine sifting, therefore, may be valuable in per- 
manent laboratories for experimental work, they generally are 
neither economical nor more reliable in ordinary routine. 

Size and Shape of Sieves. — Cement sieves are usually circu- 
lar in shape, and 6 or 8 ins. in diameter. Those advocating 
the use of the larger sieve claim that the area of the smaller 
size is such that the time required for making a test is unnec- 
essarily prolonged. On the other hand, those favoring the 
six-inch sieve claim that the larger sieve is more difficult to 
manipulate, is less likely to contain uniform cloth on account 
of its greater area, and also, unless its sides are very heavy, is 
more liable to become distorted in use, thus either breaking 
the cloth, or, by stretching, rendering it inaccurate. Since both 
of these claims have undoubtedly good foundation, the author 
has compromised on a seven-inch, which is found, in a large 
measure, to overcome the objections made to both the other 
sizes. Of course, this applies only to the Xo. 200 sieves; for 
the Xo. 50 and Xo. 100, six inches is amply sufficient. Al- 
though cement sieves almost universally are circular, it is, nev- 
ertheless, sometimes claimed that square sieves are preferable 
on account both of the greater ease of mounting the cloth on 
them squarely in the first place, and also because they are less 
liable to become distorted. If, however, care is taken when 
purchasing sieves to see that the cloth is properly mounted, 
and that the sides are sufficiently heavy, this objection becomes 
trivial. 

Two and a half or three inches is a convenient depth for 
sieves, the cloth being placed half an inch from the bottom. 
The No. 200 should also be provided with a closely fitting pan 
about two inches deep. 



FINENESS. 73 

Treatment and Size of Sample. — It is frequently recommended 
that samples should be dried^^^ before testing for fineness, al- 
though the only advantage gained by this process is a slight 
increase in the actual speed of sifting, the results being prac- 
tically unaffected. On the other hand, it involves the use of a 
drying oven, which takes time to operate, and money to in- 
stall, and only adds one more item to the already too compli- 
cated program of cement testing, so that for routine work it 
is not advantageous. The only necessary preliminary treat- 
ment of the sample is when the cement is lumpy, or when for- 
eign matter such as splinters from the barrel has become mixed 
with it, in either of which cases the material should be sifted 
through a coarse sieve, about 20-m.esh, before being weighed. 

Although 100 grams are generally taken for making the fine- 
ness test, most experienced operators find 50 grams amply 
sufficient. The time of sifting is practically halved by this re- 
duction in the size of the sample, and at the same time the ac 
curacy obtained is all that is necessary. 

Necessary Degree of Accuracy. — It is the practice of most of 
the manufacturers to report the results of the fineness test to 
the nearest per cent. The majority of Government and mu- 
nicipal laboratories report to a tenth per cent., while many 
carry their results to hundredths. In one case, the author saw 
the report of a small field laboratory in which the results w.tc 
given to three places of decimals. 

In this connection a test recently made by the author is of 
interest. Ten samples of cement were taken from ten different 
bags in the same car-load shipment, and presumably fri)m the 
same bin at the works, and each sample was siftcil separately 
to see what variation existed in the cement itself. The cement 
was a rotar\ Portland of high rei)Utation. 'Hie sittings were 
made with extreme care and check tests made to insure the 
greatest accuracy possible. The results (obtained are given in 
Table XVI., and show a range of 0.7% on the No. loc^ sieve, 
and 2.3% on the No. 200. Is it not absurd to rejiort results to 
hundredths or even tenths, when tlie cement itself on the \\nc 
sieve shows a variation of over 2%? 

It will be found upon investigation, that c\cu the most ex- 
perienced operators rarel\' work with a ])r()bal)le error ot less 

*See Appendix A. 



76 



PRACTICAL CEMENT TESTING. 



than one-half of one per cent., so that generally this may be- 
taken as the limit of accuracy in tests of fineness by sifting. 
Placing the linnt this low has also the advantage of making 
check tests and duplications more easy. It is very hard for any 
two operators to agree as to when the sifting is complete, if 
it is carried to tenths or hundredths, but the point where the 
residue cannot be reduced by more than a half per cent, is 
comparatively well marked. 

Methods of Operation. — Although the manipulation of cement 
sieves appears to be comparatively simple, it is nevertheless 
surprising to find how many operators naturally take the in- 
accurate or the tedious method. If, however, the method is 



TABLE XVI. — Showing Variation in Fineness in Different Bags of Same 
Shipment. (Tests by the Author.) 



No. 



Variation 





Fineness 


_^ 


No. 50 


No. 100 


No. 200 


02 


8.1 


19.7 


03 


8.4 


20.6 


0.2 


8.4 


20.8 


0.4 • 


86 


21.2 


0.4 


8.7 


22.0 


0.2 


8.3 


20 2 


0.4 


8.8 


21.8 


0.3 


8.2 


20.0 


0.3 


8.7 


21.6 


0.2 


8.2 


19.9 



0.7 



based upon the following considerations, it cannot go far 
wrong : 

The residue on the sieves should always be weighed — not 
the amount passing through. No matter how carefully the test 
may be conducted, some of the fine powder is certain to escape, 
amounting in some instances to as much as one per cent. This 
lost powder is almost entirely that part which passes the Xo. 
200 sieve, hence the reason for weighing the residues. 

The method should be so arranged that the point of comple- 
tion can be readily observed. This may be accomplished by 
sifting over a sheet of paper, so that the amount passing the 
sieve can be seen at once, or if a pan is used, it should be 
emptied frequently so that the progress of the sifting may be 
noted. 



FINENESS. -j-j 

Sifting simultaneously through a nest of sieves is not ad- 
-visable. In the first place, when nests are used, there is a 
tendency for the fine powder to drift back through the various 
sieves, thus making clean sifting very difficult. Again, the nest 
is much more difihcult to operate that a single sieve. Also, 
it is a longer method, since the greater part of the samxple must 
pass through all three sieves, whereas, in sifting separately, 
only the residue from one sieve is put through the next. Of 
course, when using the sieves separately, the operation should 
begin with the finest sieve. Notwithstanding the obvious 
diminution of labor obtained by sifting in this order, it is re- 
markable how many operators start with the No. 50, thus 
wasting considerable time and effort. 

The use of shot or pebbles, on the sieves, to force the ce- 
ment through more quickly, is permissible. Tests have fre- 
quently been made to ascertain whether the grinding action so 
produced is appreciable, and it has been found that in no case 
does it amount to more than a couple of tenths of a per cent., 
although their use often halves the time of manipulation. 

Common Sources of Error. — The most common sources of error 
in determinations of fineness are : Flaws in the sieve. This 
can only be obviated by careful watching. The sieves should 
be carefully examined every day before making the tests, and 
those showing flaws should either be. discarded, or, if the flaw 
be small, stopped with solder. A No. 200 sieve carefully used 
should last for 300 to 400 tests. 

Loss of powder : This is always due to carelessness in 
manipulation. The operator making these tests should be a 
man sufficiently conscientious to repeat his work in case he 
spills an appreciable amount of the material. 

Weighing amount passing sieves instead of residues : As 
previously stated this procedure will consistently lower the re- 
sults from one-half to one per cent. 

The Author's Method. — The sieves are circular. i\ ins. in 
height ; the Xo. 200 sieve is 7 ins. in diameter, while the Xo. 
50 and Xo. 100 are 6 ins.; the pans are 2 ins. in depth. The 
wire cloth is made to conform with the specificatiims mi page 
70. 

The cement, if lumpy, or if containing foreign matter, is 
first sifted through a No. 20 sieve, and anv small lumps pass- 



78 



PRACTICAL CEMENT TESTING. 



ing through are crushed. Fifty grams of cement are then care- 
fully weighed on a balance sensible to about five centigrams 
(see Fig. 36'''), and placed on a No. 200 sieve, with a pan at- 
tached. The operator grasps the sieve in one hand, so that 
it slopes upward toward the other hand, which gives it a rapid 



^^^^^^m^A ' iflfe^^>^ ^^^tfHii '' ^^9 


1 




^^^Z T7T^7 ^---^ 


1 




i^l 






H^^Bl 



Fig. -.( 



Scales for the Fineness Test. 



succession of rather sharp blows ; care must be taken to slant 
the sieve so that the cement is evenly distributed. It also 
must be struck squarely on the side, since hitting on the top 
or bottom tends to throw out the material. When most of the 
fine powder has passed 
the sieve, the pan is 
emptied, replaced, a few 
ounces of shot poured 
in and the sifting- con- 
tinued. This quickly 
forces the remainder 
of the powder through, 
and a point is soon 
reached, where it is 
impossible to reduce 
the residue by a half of 
a per cent, even after 
long sifting. The pan F^g. sy.-Special Scales for the Fineness Test. 

is then emptied and placed under a No. 20 sieve, through which 
the residue is poured, thus freeing it from the shot. The resi- 

* Figure 37 shows another form of balance especially designed for this teat. 
Using 50 grams, the beam is so graduated that the residue or amount paa-sing may 
be read directly. 




FINENESS. yg 

due is then weighed and placed on the No. loo sieve, where 
the operation is repeated. The determination for the No. 50 
is made similarly, except that in this case it is not necessary 
to use shot. It is convenient, when using 50 grams, to have 
the weights of the balance marked double their real value, so 
that the amount of residue gives the percentage directly. 

Sifting through the No. 200 sieve by this method takes on 
an average 5 or 6 minutes ; through the No. 100 about a min- 
ute ; while 3 or 4 shakes wall be sufficient for the No. 50. The 
total time occupied in making a complete determination of fine- 
ness is thus about 8 or 10 minutes. With an experienced 
operator, the tests can be considered accurate to the nearest 
half per cent., although they are reported to the nearest two- 
tenths. 

Interpretation of Results. — In considering the results of the 
fineness test, it must be remembered that fineness is not an end 
in itself, but only the means to an end, its purpose being: to 
ensure the soundness and increase the strength of the material. 
Unless, therefore, the material is exceedingly coarse, it is gener- 
ally unwise to reject a shipment on the fineness test alone, if it is 
otherwise satisfactory. The manufacturer should be notified, 
however, and if future shipments show no improvement that 
brand should be prohibited on the work. 



CHAPTER VIII. 
TIME OF SETTING. 

Definitions. — When cement is mixed into a paste with water, 
and allowed to stand, it gradually loses its plasticity and be- 
gins to offer resistance to external forces. When this resist- 
ance is complete and the material is ruptured by an attempt to 
change its form it is said to have "set." The increase in 
strength afterwards acquired is known as "hardening." These 
two actions are more or less independent, there being no fixed 
relation between them. 

From a physical standpoint, two stages in the setting may 
"be recognized : — first, when the mass begins to offer re- 
sistance, and second, when this action is completed, or when 
the mass cannot be appreciably distorted without rupture. In 
practice, these stages are termed "initial set" and "hard set," 
and determinations of time of setting are made to ascertain 
the time required for a cement paste to reach these two critical 
points. 

Objects of Test. — That a cement paste or mortar should set 
within dciinite limits of time is a practical consideration rather 
than. one affecting its strength or permanence. In actual con- 
struction, a cement should not have begun to set before being 
placed in the work, since any subsequent working of the mor- 
tar, unless thoroughly retempered, tends to break up the crys- 
tals already formed, thus weakening it, and also rendering it 
more susceptible to disintegration. A partially set mortar 
also will not flow as easil} into the voids of the aggregate 
thus making a poorer bond. On the other hand, after it has 
been placed in the structure, it should set and harden as quick- 
ly as possible so that it can offer a definite resistance to any 
external forces which might destroy it if still plastic. The best 
cements, therefore, should be slow in acquiring initial set, but 
after having reached that point, should become hard set quick- 
ly, and hence specifications usually give a cement a minimum 
time for acquiring initial set, and a maximum for hard set. 

Theory of Setting. — The chemical processes involved in the 



TIME OF SETTING. gl 

setting and hardening of cement are not yet definitely known. 
''M. Fremy* considered Portland cement to be very complex 
in composition, and ascribed the setting to the action of lime 
upon certain puzzolanic compounds, composed of double 
silicates of lime and- alumina, the calcination of the clay giving 
rise to a porous material which absorbs the lime by capillary 
afifinity." 

"M. Landrin concluded that a substance corresponding to 
the formula 3 SiO., 5 CaO is found in both Portland cements 
and puzzolana, and he considered this to be the active element 
in the hardening of cement, although he states that aluminate 
of lime contributes to the setting and accelerates that action." 

"Prof. Le Chatelier, from his study of Portland cements, ex- 
plains the phenomena of setting by showing that certain salts, 
including the aluminate and silicate of lime which form the 
active elements of Portland cement, while soluble in an anhy- 
drous state, form insoluble salts when hydrated. When they 
come into contact with water in mixing mortar the anhydrous 
salt enters into solution, then, becoming hydrated, the hydrate 
is precipitated from the saturated solution in a crystalline 
form. Those salts which are thus capable of being dissolved in 
an anhydrous state and then becoming hydrated arrive at sta- 
bility in two ways — by decomposition and by combination." 

'The tricalcic silicate, which is the essential element of 
Portland cement, is decomposed in presence of water to a hy- 
drated monocalcic silicate and a hydrate ; thus 

SiCCa, + Aq -= SiO„ CaO, 2.5 H,0 + 2 CaO, H,0." 

"The monocalcic silicate crystallizes in the form of needle- 
like crystals and the hydrate in hexagonal lamina visible to the 
eye. The tricalcic aluminate is hydrated by simple combination 
with the water. 

ALO.Ca, + Aq = A1,0„ 3 CaO, 12 TT,0." 

Mr. Clifford Richardson describesf the selling of oemcnl 
as follows: "On the addition of water to a stable system 
made up of the solid solutions which compose Portland cement, 
a new component is introduced which innnediately results 111 
a lack of ecjuilibrium, which is only brought about again by 

♦From Spalding's "Hydraulic Cement." ,, a 

f'The Se<;inK or Hydration of Portland romonl." a i>ap.M- road b.Mon- luo As- 
sociation of Portland Cement Manufacturers. Dee. U. lli>01. 



82 PRACTICAL CEMENT TESTING. 

the liberation of free lime. This free lime, the moment that it 
is liberated, is in solution in the water, but owing to the rapidi- 
ty with which it is liberated from the aluminate, the water soon 
becomes supersaturated with calcic hydrate, and the latter crys- 
tallizes out in a network of crystals which binds the particles 
of undecomposed Portland cement together. From the char- 
acteristics of the silicates and aluminates it is evident that the 
latter are acted upon much more rapidly than the silicates, 
and it is to the crystallization of the lime from the aluminates 
that the first or initial set must be attributed. Subsequent 
hardening is due to the slower liberation of lime from the 
silicates. If the lime is liberated more rapidly than it is pos- 
sible for it to crystallize out from the water, expansion ensues 
and the cement is not volume constant." 

'The set of Portland cement is almost entirely due to the 
decomposition of the alit alone. Examination of a thin section 
of a neat Portland cement mortar will show that it contains 
large quantities of unattacked celit and a certain amount of 
unattacked alit.'' 

"The strength of Portland cement after setting is due en- 
tirely to the crystallization of calcium hydrate under certain 
favorable conditions and not at all to the hydration of the 
silicates or the aluminates, since in this act of hydration noth- 
ing can take place which would tend to bind these silicates 
and aluminates together. Celit is certainly decomposed to but 
a slight degree in the process of setting. From this we may 
infer that the strongest cement is the one which contains the 
smallest amount of celit and such a conclusion is entirelv justi- 
fied by experience." 

Effect of Composition. — Since the aluminates are chiefly ac- 
tive in the setting of cement, it follow^s naturally, other things 
being equal, that the higher the percentage of alumina present 
the c|uicker will be tiie setting. Since the majority of Portland 
cements run rather high in alumina, and since they are re- 
quired to be very finely ground, which also accelerates the set- 
ting, under normal conditions they would set so quickly as 
to be entirely unfit for use. In order to retard the setting, 
it is now common practice to add one or two per cent, of gyp- 
sum, or plaster of Paris, to the finished cement. This admix- 
ture is generally made immediately before the final grinding. 



TIME Of SETTING. 



83 



SO that the mixture is a thorough one. The effect of this ad- 
dition of sulphate of hme on the setting and strength of ce- 
ment is of such importance that the following researches of 
M. Chandlot* are given at some length : 

''Setting. — The retardation of set caused by the addition of 
gypsum to cement varies according to the quantity of gypsum 
employed" (see Table XVIL). 

''But the action of gypsum on the setting of cement is not 
always permanent, and it very often happens that if a cement 
containing an admixture of gypsum is gauged a long while 
after the g>psum has been added, it sets very quickly; this 
effect is produced particularly with cements which set very 



TABLE XVII.— Effect of Gypsum on Portland Cement. 

(Tests by Chandlot ) 



Quantity of Gypsum 
Added 


Set of the Neat Cement with Fresh Water 


1 


2 


3 


Initial 

Set 


Hard 

Set 


Initial 
Set 


Hard 

Set 


Initial 

Set 


Hard 
Set 


Per Cent. 

0.0 
0.5 
1.0 

J-5 
2.0 

3-^ 
40 


H. M. 

7 
50 
2 40 

2 57 

3 (^ 
3 
3 30 


H. M. 
22 

2 43 

4 50 

5 17 
5 2,^ 
40 
7 


H. M. 

7 
10 

3 50 

3 50 

4 20 

3 45 

5 


H. M. 

15 
17 

5 

5 

6 45 

7 
7 ^ 


H. M. 

2 

2 

1 30 

3 20 

5 
5 


H. M. 

5 
5 
2 35 
5 15 
7 
7 
7 



quickly when they have no admixture of gypsum, and wliicli 
after the gypsum has been added, have been exposed to the 
air for several days" (see Tabic Will.). 

"When a cement is preserved from cc^ntact with air. the sot 
may again become (juick after a lapse of a very long period. 
Table XTX. shows cement mixed willi jVr of g\i)sum, and j>re- 
servcd in an air-tight flask." 

"Cements containing an adniixinre oi gypsinn. i>reseiU iliis 
peculiarity, that they often set more rapidh when ganged with 
sea water, than when gauged with fresh water." 

"When a cement containing gypsum has bei-n exposed io 

♦From "Clment^ pt Thaiix ITydiMuliqiics," hy K riuiinllot. Tnin.Hlallmi from 
Butler'H "Portland Coniont." 



84 



PRACTICAL C EM EXT TESTIXG. 



the air and has become quick setting again, it sets quicker when 
gauged to a thin consistency with an excess of water, than 
when it is gauged to a stiff paste with very little water. This 



3- 



TABLE XVIII.— Effect of Gypsum on Portland Cement. 
(Tests by Chandlot.) 

Description of Cement 

Cement Mixed with 3 Per Cent, 
of Gypsum — 

Tests made the same day.... 
4 days after. 

7 
II 

15 
19 
24 
32 
41 
Cement Mixed with 2 Per Cent. 
of Gvpsum — 

lests made the same day. . . . 

" 12 days after. . . . 

21 " .... 

Cement Mixed with i Per Cent. 

of Gypsum — 

Tests made the same day. . . . 
8 davs after. . . . 

15 ' " 
Cement Mixed with i Per Cent, 
of Gypsum — 

Tests made the same day. . . . 
" 8 days after. . . . 

-3 .... 

30 



Set with Fresh Water 

Initial Set Hard Set 


H. 


M. 


E. 


M. 


I 





7 








5 


2 


15 





5 





20 





8 





30 





5 





30 





7 





35 





5 





25 





10 





30 





45 


5 


30 


5 





19 





4 


40 


14 








18 





50 


5 


30 


8 


30 





18 


2 


30 





II 





20 


6 





9 


30 


4 


30 


8 








15 





30 






7 






TABLE XIX.— Efifect of Gypsum on Portland Cement. 
(Tests by Chandlot.) 



Tests made the same day. 
" I month alter. 

" 2 " '• 

5 " 



^Initial Set^ 
H. M. 


^Hard Set^ 
H. M. 


3 

2 50 
I 30 
10 


6 25 
5 

7 
18 



is contrary to that which always takes place with cements 
not containing admixtures of gypsum.'' 

"Strength. — The addition of small quantities of gypsum to 
Portland cement results in increasing its strength. When, 
however, a cement is kept in sea water and the proportion of 
gypsum added exceeds one to two per cent., the mortar is not 



TIME OF SETTING. 85 

long before It shows traces of alteration, and the briquettes 
are sometimes completely disintegrated" (see Table XX.). 

'Tf the cement containing gypsum is allowed to remain in 
sacks for several weeks, it develops very poor strains at the 
early dates of testing" (see Table XXL). 

"As a result of a considerable series of chemical researches 
in the matter, M. Chandlot comes to the conclusion that the 
peculiar effects of adding gypsum to Portland cement are due 
to the formation of a sulpho-aluminate of lime, a salt which 
he succeeded in producing artificially, and to which he attributes 
the formula (AI2O3, 3 CaO) 2.5 (SO3, CaO). From this he de- 
duces the following theory : 

'Tt is well known that aluminate of lime is insoluble in a 
saturated solution of lime. If then, sulphate of lime and free 



TABLE XXII.— Effect of Gypsum on Portland Cement. 
(Tests by Chandlot.) 

r» ■ 1 A£i TTTv,- V o , £ Matters in Solution Per Litre of 

Periods After Which Samples of Liquid in Grammes 

the Liquid Were Taken. ~„„ ai o cr* r>^e\ 

CaO. AI2 Oa. bOs CaO. 

Gk. GB. 

10 minutes 1085 Nil i 734 

3 hours 1.085 ■* i ^32 

6 " 0.875 " ^632 

12 " 0930 •• 1504 

8 days 1.085 " Nil 

I month 0.304 ** " 



lime are present, together with aluminate of lime, it follows 
that the combination of the sulphate of lime with the aluminate 
can take place but very slowly, because the aluminate cannot 
become hydrated on account of the immediate solution of the 
lime. Thus, a mixture of powdered aluminate of lime, o\ sul- 
phate of lime and of slaked lime, having been sliaken with an 
excess of distilled water, produced the results given in Table 
XXII." 

"The above shows that the combination of the sulphate with 
the aluminate only takes place after a considerable period, the 
aluminate becoming hvdrated but \ery slowly." 

*Tn Portland cements of the best nianufacluro. tlure always 
exists a little free lime, and as llie\ contain very liiilc alumina, 
this free lime, by rapidly dissolving, prevenls t1u> hydration of 
the aluminate; the sulphate of linn- bcconnng (Hssolved in 



86 



PRACTICAL CEMEXT TESTLXG. 



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TIME OF SETTING. 



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N ro ro ro 
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gg PRACTICAL CEMENT TESTING. 

turn, and not being able to combine with the aluminate, adds 
its action to that of the Hme in annulhn-g the function of the 
aluminate ; as it is to this salt that setting is attributable when 
it takes place rapidly, a slow-setting cement results." 

"If the free lime, by being sufficiently exposed to the air, 
becomes carbonated, at the moment when the cement comes 
into contact with the water, the lime dissolves less freely, and 
nothing prevents the solution of the aluminate ; the combina- 
tion with the sulphate of lime can take place, and the sulpho- 
aluminate formed, as well as the excess of aluminate, by crys- 
tallizing, determine the rapid setting of the cement." 

Effect of Age. — When cement is allowed to stand exposed to 
the air and to dampness, it gradually absorbs water and car- 
bonic acid. This absorption and consequent hydration affects 
the aluminates more readily than the silicates, so that cement 
thus exposed gradually becomes slower setting, until eventu- 
ally it loses all of its hydraulic properties, although well pro- 
tected cement may be stored several years without appreciable 
deterioration. Generally speaking, however, it may be said 
that the tendency is for a cement to become slower setting with 
age, the only exception being in cases where a high percentage 
of sulphate of lime is present (see page 83). 

Table XXIII. gives the results of a series of tests made by 
the author to demonstrate this action. The cement was a high 
grade rotary Portland, and was kept in its original package in 
the air of the laboratory, all tests being made at a uniform 
temperature. 

Effect of Mixing Water. — Since the setting of cement is 
caused b\ a solution and subsequent crystallization of certain 
of its ingredients, it follov.s that the greater the amount of 
water present, the longer the time it will take for it to reach the 
saturated condition necessary for crystallization. The effect of 
different percentages of water on the setting may be clearly 
seen in Tables XXIV. and XXV. 

The temperature of the water also affects the setting, in- 
creased temperatures accelerating the rate of crystallization. 
Spalding"^ says : "Below a certain inferior limit, ordinarily 
from 30 to 40 degrees Fahr., the mortar sets with extreme 
slowness or not at all ; while at a certain upper limit, in some 

♦"Hydraulic Cement," by F. P. Spalding, p. 65. 



TIME OF SETTING. 



89 



TABLE XXIII.— Effect of Age on Time of Setting. 
(Tests by the Author.) 



Age of Cement 

Original 

1 month .... 

2 months 

3 " 

4 " 

6 " 

9 " 



/-Time of Setting- 

(in minutes) 

Initial Hard 



32 

35 
41 
61 
92 
106 
135 



179 

173 
226 
240 
265 
330 
358 



Age of Cement 

1 ^'ear 

1%, years 

2 " . . , . 

2% ^' .... 



-Time of Setting-v 

(in minutes) 
Initial Hard 


182 


420 


209 
267 
303 


510 

600+ 

600-1- 



TABLE XXIV. — Influence of Amount of Mixing Water on Time of Setting. 
(From Sabin's "Cement and Concrete.") 

Per Cent. Water, by Weight. 24 26 28 30 32 34 36 

T, ^, J CTime of Setting (minutes) 

Portland 1 t •.• 1 c . 00 

P -^ Initial Set 2 2 3 7 2r 28 38 

i^ement ^ ^^^^ g^^ ^^^ ^^^ ^^^ ^^^ ^^^ ^^^ ^^^ 

Per Cent. Wa^er. by Weight. 26./ 28.6 30.8 33.3 36.4 40.0 .... 
Natural C^^^^^ °^' Setting (minutes) 

Cement^ Initial Set 20 23 30 42 46 55 

cement ^ Hard Set 28 41 57 76 78 85 .. 



TABLE XXV. — Showing Effect of Amount of Mixing Water on Time 
Setting, and Also a Comparison of the GiUmore and Vicat Needles. 
(From Watertown Arsenal Report, 1901.) 

-Time of Setting- 



of 



Brand 



C. 

(with plaster) 



(without pla:Jter) 



D. 



Per 

Cent. 

of 
"Water 

( 20 

25 

( 30 

( 20 

• 25 
( 30 
( 20 

25 
( 30 
( 20 

( 30 
( 20 
25 
( 30 
( 20 

• 25 
( 30 



WithCxill 
Initial 
H. M. 


more Wires 
Hard 
H. M. 


2 


20 


5 


00 


3 


20 


7 


30 


5 


40 






4 


"5 


7 


10 


5 


10 


8 


05 


7 


00 






2 


10 


4 


25 


4 


35 


6 


00 


5 


45 









('5 





15 





35 


4 


55 


5 


10 


8 


35 


I 


4<) 


5 


i<) 


4 


15 





"5 


4 


5" 


7 


i<) 





3" 


4 


35 


4 


10 


6 


40 


5 


35 


8 


05 



'"'With Vicat Needle 
Initial Hard 
H. M. H. M. 


35 


4 25 


2 5^^ 


t^ 35 


4 40 


S 40 


2 4=; 


10 


35 


7 ^>5 


5 3^^ 




qo 


^ lO 






'^S 





10 





\o 


3 


30 


3 


1 5 


6 


5^^ 


1 


jS 


4 


44 


;, 


25 


1; 


4»^ 


4 


3.> 


() 


53 


t) 


<>S 


.> 


40 


^ 


|(> 





10 


4 


5^' 


7 


20 



90 



PRACTICAL CEMEXT TESTIXG. 



cements between lOO and 140 degrees Fahr., a change is sud- 
denly made from a very rapid to a very slow rate, which then 
gradually decreases as the temperature increases, until prac- 
tically the mortar will not set." For the small ranges ordinarily 
occurring in routine testing, however, say between 65 and /^ 
degrees Fahr.. the effect is usually negligible. 

Effect of Fineness. — :It is obvious that a finely ground ma- 
terial will be more quickly attacked by a solvent than a coarse 
one, so that a fine cement is almost invariably quick setting un- 
less artificially retarded, even in cements thus treated the finer 
being generally the quicker setting. Table XXVI. gives the 

TABLE XXVI. — Influence of Fineness on the Time of Setting of 

Portland Cement. 

(From Butler's ''Portland Cement.") 

<5!.TnTiio ' Fineness • — Time of Setting — » 

oampie g^^ Treated Residue on in minntes 

^^- No. 50 No. 76 Xo. 180 Initial Set Hard Set 

fAs received o.o 6.0 22.4 25 45 

\Reground 00 0.0 Tr. i 5 

• As received 2. 7 10. o 26.6 30 go 

(Reground 0.0 0.0 Tr. 6 15 

( Ac; rerf^ivprl ir " fi '> \ \ in T7 

3- 



(As received 1.5 7.6 24.4 30 120 

Reground 0.0 0.0 Tr. 7 15 



<^As received 1.2 6.7 30.0 20 6o 

'^ "(Reeround 0.0 0.0 Tr. 2 10 

CAs received. i.o 9.3 28.4 15 30 

^' (Reground 0.0 0.0 0.6 I 10 

^ CAs received 0.5 7.7 26.4 Undefinable 360 

\ Reground 0.0 0.0 0.4 8 25 

< As received 0.8 3.0 iS.o 15 240 

'■ "(Reground 0.0 0.0 0.4 2 240 

r. (.\s received 7,. 6 16.0 34. S 20 30 

( Reeround 0.0 0.0 1.6 2 5 

results of tests showing the effect of regrinding cements on 
the time of setting. The acceleration of the setting in this case, 
however, is not entirely dependent _on the fineness, but also 
on the seasoning, since the interior of the coarse particles con- 
tains fresh material practically unseasoned, while the original 
fine material has passed the early stage of rapid setting. To 
determine the effect of fineness alone, a clinker should be 
ground, at the same time, to different degrees of fineness, and 
the time of setting determined, in which case the variable intro- 
duced by seasoning would be eliminated. 

Effect of Exterior Conditions. — Of the different exterior con- 
ditions affecting the setting of cement, temperature and hu- 



TIME OF SETTING. 91 

midity are by far the most important. Increased temperature 
tends to accelerate the crystaUization and make the setting 
rapid, while increased humidity tends to retard it. High tem- 
peratures generally quicken the rate of setting whether acting 
before or during the test, so that if a sample of cement is ex- 
posed to an excessive heat its setting is usually accelerated, 
even if it be cooled to normal temperature before the deter- 
mination is made. For this reason, shipments_ of cement made 
in summer will often be slow setting when leaving the manu- 
facturers and quick when arriving on the work, the heat in 
the cars having brought about this condition. The tempera- 
ture of the laboratory exercises the same influence, as can be 



TABLE XXVII.— Influence of Temperature on the Setting of Portland 
Cement. (From "Butler's Portland Cement.") 



Sample 


100° 


80^ 


60° 


400 


100° 


80° 


6O0 


40° 


No. 
I. 




T-ri^ + iol a^* ;■" ly/ti-^-.-t-^r. 












1-5 


4 


6 


13 


125 


1-5 


2 


2-5 


2. 


3 


5 


6 


8 


I 


125 


1-75 


2.5 


3- 


4 


10 


15 


20 


0-5 


0.75 


1-5 


t>5 


4.* 


5 


9 


15 


30 


05 


0.75 


I 


6 


5- 


6 


10 


14 


25 


I 


1-5 


2 


2-5 


6.* 


7 


12 


15 


20 


1-75 


2 


2.25 


2.5 


7 * 


9 


10 


15 


17 


3-5 


6 


7 


12 


8. 


10 


15 


35 


40 


0.75 


I 


I 25 


1-75 


9- 


II 


15 


20 


57 


3 


5 


6 


10 


JO. 


II 


13 


15 


30 


2-5 


3 


3-5 


6 


II. 


19 


32 


60 


120 


3 


6 


7 


15 


12. 


15 


35 


70 


360 


3-5 


6 


7 


22 






* 


Adulterated with Kentish Rag-stone. 







seen from Table XXVII. The efifect of dampness on cement 
prior to the test, as has been shown, is to season it and thus 
retard its set. The same action also is apparent durini;- Mic 
tests, those made in a damp atmosphere being much sloAor 
than those made in dry air. Test specimens stored in a d nnp 
closet, accordingly, will set slower than if kept in (lr\ air. 

Rise of Temperature." — The rise of teni])erature in conuMU 
pastes during setting has i^een the subject of freciuem contro- 
versy, some engineers having gone to tiie length of stating 
that the only necessary specification to ensure a gcHul material 

•For comiirehensive datca on the riso in tompcrature of mortars and t'onrretes. 
the reader is referred to the ileport of tlu> Watertowu Arsenal. "Tests of Metals, 
etc.," for 1901. 



92 



PRACTICAL CEMENT TESTING. 



was that it should show no appreciable temperature rise in 
setting. The reason for this was that the rise in temperature 
was supposed to be a direct measure of the so-called "free 
lime" in the cement. As a matter of fact, however, it is due 
more to the heat of crystallization of the normal ingredients, 
and its amount will generally be found to be a function of the 
time of setting. If, therefore, a cement is so made that it will 
develop no heat, it must, of necessity, be very slow setting, and 
to be brought to this condition, the majority of cements would 
require the addition of an excessive amount of sulphate of 
lime. 

It has been suggested that the time of setting be measured 
by temperature rise, the time taken to reach the maximum be- 
ing called initial set, and the return to the normal, hard set. 
This, however, has been proven impracticable, both by reason 
of the variable introduced by the presence of free or loosely 
combined lime, and also by reason of the very small rise oc- 
curring in slow setting cements, which would make readings 
of time very dif^cult, if not impossible. The author determined 
this rise of temperature on every sample of cement tested in 
the Philadelphia Laboratories for over four }ears, and at the 
end of that time abandoned the test as not oaly inconclusive^ 
but also as often actually misleading. 

The rise in temperature of a paste of normal cement, in a 
mould the size of the ring used with the Vlcat needle, will be 
found to average from 3 to 5 degrees Fahr., and also since 
its amount varies more or less with the time of setting, the 
effect of age, temperature, fineness, etc., will be similar. 

Normal Consistency. — Since the amount of water used in mix- 
ing exerts considerable influence on the time of setting, it fol- 
lows that this percentage must be definitely fixed and not left 
to the discretion of the operator. Some specifications, nota- 
bly those of the U. S. Army Engineers, require that all ce- 
ments be mixed with the same amount of water, but on ac- 
count of the varying composition and other characteristics of 
different brands the consistency of the pastes so obtained will 
be quite variable, and since it has been determined that the 
action of different cements is more nearly similar when gauged 
to a definite consistency, rather than with a fixed amount of 
water, the plasticity or the consistency of the paste should al- 



TIME OF SETTIXG. 93 

ways be uniform. This "normal consistency" can be obtained 
by several methods, the three foUowmg being those most gen- 
erally employed : 

The Ball Method. — The consistency obtained by this method 
is such that if a ball of the paste, about two inches in diamcLcr, 
be dropped upon a hard surface from a height of two feet, it 
will not crack nor flatten to more than half its original thick- 
ness. This determination is extremely simple and easy to make, 
gives a consistency readily distinguished and suitable for mould- 
ing into any form, and for an experienced operator, is accu- 
rate to one-half of one per cent. 

By the Vicat Needle. — (See page 94.) This method requires 
a consistency such that a cylindrical plunger, one centimeter m 
diameter and of 300 grams weight shall penetrate a definite 
distance into the paste contained in the rubber ring. The 
French Commission on Methods of Testing, recommended that 
this penetration be 34 millimeters : the Committee of tlie 
American Society of Civil Engineers advises 10 millimeters, 
while a consistency corresponding with that obtained by the 
ball method will be found to be about 7 or 8 millimeters. Al- 
though this method is somewhat more accurate than the ball 
method, it is much more tedious, usually requiring several trials 
before the proper consistency is obtained, and is often impos- 
^sible for quick setting cements. 

The Fluid Method. — This method originated in the Ro}al 
Testing Station of Charlottenburg and consists of mixing the 
cement to a syrupy paste so that it will run from the blade of 
a spatula (6 x i^ ins.) in long thin threads without forming 
lumps. Representing the amount of water required to bring 
the paste to this consistency by N, then the percentage to be 

If . N + I , . N 4- 3 ^. 

used for neat pastes is , and for i : 3 sand - . bo lar 

'2 ^4 

as the writer's experience has gone, however, this method is 

not as accurate as either of the two preceding, there being even 

greater room for diflference of opinion as to when the cement 

will just run off the knife without forming Umips than as to 

when the ball or the ])lunger behaves properly. This method 

in common with the Vicat has the disadvantage o\ re(|uiring 

a separate determination, whereas in following the ball 



94 



PRACTICAL CEMENT TESTING. 




Fig. 38. — The Vicat Needle 



method the consistency determination 
can be made in connection with the 
other tests. 

Consequently, in routine work, the 
ball method is g^enerally preferred as 
being- quick, convenient and sufficiently 
accurate. If it is desired to use the con- 
sistency recommended by the Committee 
of the American Society of Civil En- 
gfineers, that of the ball method plus one 
per cent, will be found near enough for 
all practical purposes. 

Forms of Apparatus. — But two forms 
of apparatus are used in the United States 
for routine determinations of time of set- 
ting- — the Vicat and the Gillmore needles. 

The Vicat needle, shown in Figure 38, 

consists of a stand supporting a needle one 

millimeter in diameter, and loaded to 

The cement paste is 



300 grams weight 
placed in a rubber mould in the shape 
of a frustrum of a cone having an 
upperdiameter of 6 centimeters, a lower 
diameter of 7 centimeters and 4 centi- 
meters in height, the mould resting: on 
a glass plate an eighth of an inch thick. 
The specimen is placed under the needle 
which is let down upon it from time to 
time, the amount of penetration being 
read from the gfraduated scale. Initial 
set is said to have taken place when the 
needle ceases to penetrate within five 
millimeters of the bottom of the speci- 
men, and hard set is attained when 
the needle ceases to indent its surface. 
For making the normal consistency 
test, previously described, the plung^er 
is substituted for the needle, the differ- 
ence in weight being compensated by 
changing the upper cap. 



'i ' 



Fig, 39. — An Improved Form, 
of Vicat Needle. 



TIME OF SETTING. 



95 



An improved form of Vicat needle, made by Jos. W. Bram- 
well, is shown in Fig. 39. The movable part, consisting of a 
square rod having the needle fastened to its lower extremity, 
weighs exactly 300 
grams and is grad- 
uated to indicate 
the amount of pene- 
tration, while for 
determinations of 
consistency, a sec- 
ond rod, terminated 
by the plunger, may 
be substituted for 
that carrying the 
needle, or, if it is 
desired, a single rod 
may be obtained, 
having the needle 
at one end and 
the plunger at the 
other. This form of 
apparatus eliminates 
the possibility of 
error due to the use of the wrong cap, and also commends it- 
self not only for its simplicity of construction and ease in manip- 
ulation but also by its lower cost. 

The Gillmore needles, shown in Figure 40, consist of two 
wires each supporting a weight, one having a diameter at the 
bottom of the wire of i/12-in. and carrying a weight of .| of a 
pound, and the other being i/24-in. in diameter and carrying 
a weight of one pound. The cement paste is moulded into a 
cake or pat, and the time observed wdien it will sustain these 
needles without perceptible indentation, the former giving the 
initial and the latter the iiard set. These needles are often fur- 
nished without a permanent mounting in which case great care 
should be exercised to apply iheni verticall} , since api)l\ing 
them at an angle will decrease the area under pressiu-e and 
hence give false results. l'\)r accurate \\<nk they shouKl al- 
ways be mounted in a frame as shown in the figure. 

For determinations of iiard set. these two forms of apj^ara- 




FiG. 40. — The Gillmore Wires. 




96 



PRACTICAL CEMENT TESTING. 



tus arc equally reliable, bul, for initial set, the results obtained 
with the \ icat are generally more accurate, the point when 
a needle ceases to penetrate a certain depth being much more 
clearly marked than the point when it ceases to indent the sur- 
face. There is a long period during which it is almost impos- 
sible to tell whether a surface 
mark is made or not, since the 
needle invariably leaves a circu- 
lar white spot, probably caused 
by the crushing- of some minute 
crystals, which may readily be 
mistaken for real penetration. 
In routine work, either of these 
forms may be used, wdth the 
preference, probably, in favor 
of the Mcat."^ In point of 
value, the results of both ini- 
tial and hard set obtained with 
the Meat needle will be found 
to average from a half to three- 
quarters of the results of the 
Gillmore wires. t 

Many contrivances have been made to obtain the time of 
setting automatically, but none of them has been found capable 
of use in routine testing. The Amsler-Lafifon apparatus (Fig. 
41) will automatically record the penetration of a needle and 
the temperature of the paste at intervals of a minute until the 
setting is complete. Cornell University has a machine in 
which a needle is moved over a trough of cement paste, re- 
leased every minute and the penetration recorded. Such 
machines, however, are constructed more for experimental pur- 
poses, their mechanism being too complicated for every-day 
use. 




Fig. 41- — The Amsler-Laffon Appar- 
atus for Automatically Determining 
Time of Setting. 



Methods of Operation. — In preparing cement pastes for this 
test it is not only necessary that they should be of a standard 
consistencv, but also that this consistencv be obtained bv a 



♦The Vicat needle is recommended by the Committee of the American Society 
of Civil Engineers. See Appendix A. 

tFor data on the comparative vaiue.s obtained from these two forms of ap- 
paratus, the reader is referred to the Watertown Arsenal Report, "Tests of Metals, 
€tc., for 1901. 



TIME OF SETTING. gy 

uniform method. The longer a paste is manipulated the wetter 
and more plastic it becomes, and, furthermore, the properties 
of cement pastes vary with different lengths of time employed 
in working, although the consistency be the same. That is 
to say, that although apparently similar, the properties of a 
cement paste mixed with a certain amount of water for a short 
time will be different from one mixed with less water for a 
longer time. For this reason a uniform method of mixing 
must be followed, and in practice, it is generally advisable to 
follow the same method as that used for the making of neat 
tensile briquettes.* 

In making pats or cakes for use with the Gillmore wires, or 
in filling the moulds for the A'icat needle, care must be taken 
that the mass of the specimen be uniform throughout. The ma- 
terial must never be tamped, or rammed, since this tends to 
create a variation in its density, and also to flush the water to 
the top, which causes errors in surface measurements. The 
American Society of Civil Engineers' Committeef recommends 
the following method for filling the moulds of the Meat needle: 

'Tn making the determination, the same quantity of cement 
as will be subsequently used for each batch in making the bri- 
quettes (but not less than 500 grams) is kneaded into a paste, 
as described in paragraph 58, and quickly formed into a ball 
with the hands, completing the operation by tossing it six 
times from one hand to the other, maintained six inches apart ; 
the ball is then pressed into the rubber ring, through the larger 
opening, smoothed off, and placed (on its large end) on a glass 
plate, and the smaller end smooched off with a trowel." 

This Committee also advises that the test pieces be stored 
in a damp closett during the time of setting, but this is gener- 
ally found to decrease, rather than increase the uniformity, on 
account of the fre(|ucnt removing of the specimens in making 
the trial tests, and, moreover, has the disadvantage of so nuich 
prolonging the time for hard set, that it often exceeds the ordi- 
nary working day. In routine testing tiiis proceeding will be 
unnecessary, provided care is taken to keep the specimens pro- 
tected from any extreme heat, the sun's rays, or a draught of 
air that would tend to dr> out the water. 

♦See page 117. 

tSee Ai)i)endix A. 

JFor description of damp closets, see page 130. 



98 PRACTICAL CEMENT TESTING. 

In operating- the Vicat needle or plunger for initial set or 
for normal consistency, the proper method is to bring it care- 
fully into contact with the surface and then quickly release it, 
and not to let it down gradually into the paste. 

The Author's Method. — A sample of 500 grams is weighed 
and placed on a mixing slab of plate glass, this quantity being 
sufificient not only for the set test, but also for the making of 
the test-pieces to be used in the soundness tests described in 
Chapter X. The cement is formed into a crater and an amount 
of water about one per cent, short of that ordinarih required to 
bring that brand of cement to normal consistenc}, poured into 
the center, the water being at a temperature of between 65 and 
75 degrees Fahr. Material from the edge is turned in with 
a four-inch trowel until the water is absorbed, and the paste 
vigorously w^orked with the hands, as dough is kneaded,* for 
a minute and a half. Additional water is then slowly added 
from a burette and mixed in, until normal consistency is 
reached, and although this process is not strictly accurate it 
introduces an error so small as to be negUgible, and saves the 
time and trouble of making a separate determination for con- 
sistency. Actual determinations on the Vicat plunger for 
normal consistency are only made at intervals as a check, an 
experienced operator being able to recognize it and gauge 
it within a half per cent, at least. The paste is then formed 
into a ball, forced into the larger end of the rubber ring of 
the Vicat needle, smoothed on the bottom, placed on a piece 
of plate glass (4 ins. x 4 ins. x ^-in.), the excess of material 
cut ofY the top and smoothed with the trowel without pressing 
or ramming. The specimen is kept in the open air of the lab- 
oratory, the temperature of which is maintained between 65 
and 80 degrees Fahr., and readings of the penetration made at 
intervals of from one to ten minutes as may be necessary. The 
records cover the percentage of mixing water, the time of add- 
ing the water, the time at which initial and hard set are attained, 
and the temperature of the room at the beginning and end of 
the test. 

It must be understood, however, that this method, while giv- 
ing sufficiently accurate results with experienced operators, 
could not be employed by a novice; for any other than an ex- 

♦The method of kneading is more fully described on page 120. 



TIME OF SETTING. gg 

pert a separate determination of consistency should always be 
made, and then the proper amount of watei added at once for 
the set test. 

Sources of Error and Accuracy. — Excluding the errors due 
to improper manipulation, which can always be traced to in- 
experience or lack of proper knowledge, the chief source of 
error in this test is the subjecting of the sample to improper 
environment. Many testers collect their samples on one day 
and test them the following, and during the night leave them 
near a radiator, or exposed to dampness so that by the follow- 
ing morning their setting properties have entirely changed. 
Testing in a room too hot or too cold, or using water of an 
abnormal temperature, is also responsible for many errors, 
while the use of impure water may produce a chemical action 
and thus introduce irregularities. In operating the Vicat 
needle care should be taken to keep it clean and straight, to 
apply it vertically, near the center of the specimen and not on 
the edges. The needle must always be brought into contact 
with the surface of the paste and quickly released ; lowering 
it slowly into the paste will invariably give a shorter period 
for initial set. 

At best, the test of time of setting can be considered as only 
approximate ; a skillful operator should work with a probable 
error of about lo per cent., but a novice will often be fortunate 
to duplicate his results within 30 or 40 per cent. 

Interpretation of Results. — On account of the approximate 
character of the determination, and the necessary presence of 
the personal equation, the requirements for setting should al- 
ways be interpreted liberally. A mortar or concrete on actual 
construction will generally, on account of the wetter mixture, 
and the presence of the aggregate, require from 2 to 4 times 
as long to set as the test-piece in the laboratory. C'oncrote 
for heavy construction usually requires about 20 minutes to 
be mixed and placed in the work, and on tlie hyi)oihesis that 
the concrete requires twice as long to set as the cement paste, 
a test of less than 10 minutes initial set would show that the 
concrete had commenced setting ])efore being tamped into 
place, and hence had been subjected to rewtM-king. although 
not retempered. CemeiU mixed in a mortar box for bnck- 



100 PRACTICAL CEMEXT TESTLXG. 

laying, or similar purposes, will often stand over an hour after 
mixing and before being used, and if this is allowed, the re- 
quirements for setting should be more rigidly adhered to. 
Generally, if the test of initial set is less than a half or a third 
of the time required to mix and place the material on the work, 
the shipment should be rejected, or held for further seasonmg. 
The determination for hard set is less important, and un- 
less prolonged beyond all reasonable bounds, so that the 
progress of the work will be delayed, rejection on failure to 
pass this requirement alone is rareh', if ever, justifiable. Gross 
failure in this test will almost invariably be accompanied by 
failure in tensile strength, on which ground it may be rejected 
without question. 



CHAPTER IX. 

TENSILE STRENGTH. 

The test of tensile strength consists in mixing cement and 
water, or cement, sand and water into a paste, forming it into 
test-specimens, called briquettes, which are allowed to set and 
harden under definite conditions, and tlien determining the 
amount of force necessary to cause rupture in tension at the 
expiration of fixed intervals of time. 

The object of the test is to obtain a measure of the strength 
of the material as used in actual work. In construction, a con- 
crete is often subjected to every conceivable form of stress, ex- 
cept, possibly, that of torsion, while the testing is confined al- 
most exclusively to tension. This condition is the outcome of 
both tiieoretical and practical considerations. \Miile it is im- 
possible to formulate definite ratios between the ultimate 
strengths of cement under difYerent forms of stress, neverthe- 
less, the tensile strength is, more or less, a measure of the 
compressive, transverse, adhesive and shearing values,* and, 
furthermore, investigations have apparently shown that the 
strength of cement in tension is more susceptible to any good 
or bad influences operating on the material, and hence fur- 
nishes a better criterion of its value than tests made in any 
other manner, the results of the tensile test thus giving the 
most reliable basis for computing the values ()f the strength 
under other forms of stress. 

The practical considerations favoring the adoption of this 
form of strength test are the small and easily handled test- 
specimens, the lower stress, as compared with compression 
tests, necessary to cause ruj)ture, and also the fact that uni- 
formity in the preparation of the specimens is (>nl\ necessary 
in a small portion of the s])ecinien, namely the breaking sec- 
tion, while accurate test-pieces lor the other determinatiims 
must be homogeneous and uniform tln-oughout their entire 
mass. 

Although in practice cement is almost in\'ariabl\ mixed with 

♦For the relations between tensile siriMiKlii and that of eompresplon. rres^;- 
breaking, etc., see Chapter XII. 



102 PRACTICAL C EM EXT TESTIXG. 

an aggregate, tests are usually made on both neat cement and 
sand mixtures. The objection to the use of test pieces of neat 
cement is that they are not similar to the conditions of prac- 
tice, while the reason that sand tests are of comparatively re- 
cent origin is that the sand introduces another variable in the 
influence exerted by its character. 

The rupture of a neat briquette takes place when the force 
exerted exceeds the sum of the cohesive strengths of the par- 
ticles of cement lying in the least section to the adjacent par- 
ticles. In a sand briquette, on the other hand, rupture is in- 
duced by failure in cohesion of adjacent cement parr.icles, by 
failure in the adhesion of the cement to the sand grains, and 
by shearing of the cement between overlapping grains of the 
aggregate. The reason that the strength of briquettes of sand 
mortar apparently exceeds the sum total of these strengths is 
that, while a neat briquette ruptures in practically a plane sec- 
tion, a sand mortar fails along an irregular surface due to the 
projection of the sand grains, so that the actual area over 
which rupture takes place is very much in excess of the cross- 
section. Xow, since the stresses producing failure in sand 
briquettes are very complex in character, and since they bear 
no definite relation to the strength of pure cohesion, and, 
moreovei , s^nce in actual construction cement is commonly used 
with an aggregate, it follows that the strength of sand bri- 
quettes furnishes a better measure of the conditions of practice. 
Neat briquettes, on the other hand, are more susceptible to 
both interior and exterior influences, and hence are better cri- 
teria of the character of the material. In other words, the sand 
tests are a measure of strength, while the neat tests are more 
a measure of quality. 

The sand mixture commonly employed for the testing of 
Portland cements is i part, by weight, of cement to 3 parts of 
sand. The periods at which the briquettes are broken have 
been arbitraril} fixed by usage at 7 and 28 days, although much 
longer periods are necessary for the accumulation of reliable 
data on experimental research. Twenty-four hour tests also 
are generalb/ made on neat briquettes, and occasionally on 
sand. Tests after 3 days are frequently made in England and 
on the Continent, but are rarely employed in this country. 

Effect of Composition. — Cement is composed essentially of 



TENSILE STRENGTH. 



103 



silicates and aluminates of lime, to which after burning is 
added a small amount of sulphate of lime. The aluminates and 
sulphates'^ are responsible for the setting and early strength, 
and the silicates for the final hardening. It follows, therefore, 
that a large proportion of aluminates, and hence usually high 
sulphates, make cements of greater early strength and, on ac 
count of the corresponding decrease in the silicates, lower 
ultimate strength. Moreover, the strength in the early periods 
of hardening, due to the aluminates and sulphates, is apparently 
not permanent in character, but is soon lost, the action being 
somewhat in the nature of a veneer on the true strength. The 
diagram (Fig. 42) rather crudely illustrates the idea, it not be- 



0; 

D 
Q 


















•frit-—- 










1 


■^ 






~~^~.^, 




/ 




■«^„^_^ 


Nea 


t i/f'iL 


r'T^ 








^ 


N 










,-«^c 


". 




^r 














s 


ll 




% 


4 








5and_ 


_Mor7 








1/ 




\ 


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Fig. 42. — Diagram Illustrating the Hardening of Portland 
Cement, Measured by Tensile Strenrtl;. 



ing intended to show actual values nor even the relative mag- 
nitude of one of the dotted curves to the other, hut only that 
the actual strength is the sum of the strengths of these sepa- 
rate ingredients. The reason for the fre(|uently occiuTing loss 
in strength found in periods of from 28 days to 1 year can be 
thus readily explained. The subse(|ucnt retrogression will be 
discussed later in this chai)ter. /Xnother inij)()r:ant factc^- in 
producing high tests at early ])erio(Is is an excess oi lime, and 
this being the case, it fre(iuently happens thai to give gooil 
specification tests, a cement is prochiced so liigh in hnie as to 
be unsound. For this reason, high tensile lesls at 7 tla\s ar(^ 



*See page 9. 



104 



PRACTICAL CEMEXT TESTIXG. 



often considered to be indicative of the presence of an abnor- 
mal amount of lime, and have occasionally been excluded in 
specifications which place a maximum as well as a minimum 
on the seven-day neat tensile test. 

Small amounts of magnesia, alkalies, etc., have little or no 
infiiience en the strength. Excess of these ingredients, or ab- 
norm:il amounts of lim.e and sulphates only affect the strength 
in airecting its sotmdncss.* since disintegration, either incipient 
or pronounced m.ust vitally influence the resistance of the ma- 
terial. 

Effect 01 Age. — The effect of the age of cement prior to test- 



TABLE XX\ III. — Enect of Seasoning on the Tensile Strength of Portland 
CemeLt. • Tests by the Author.) 

Age of Tensile Strength., Lbs. per Sanare Inch > 

Misrare Cement 24 7 28 2 4 6 12 

Before Test hours days days mos. mos. mos. mos. 

^Original 541 739 7S6 772 732 743 699 

I month 553 717 769 769 743 762 753 

Neat ^ months 504 664 69S 732 729 715 721 

Cedent '^ ^ " -^"^ ^" ^°3 "''^^ ^^-^ '°3 '°^ 

I 9 " 4S5 623 673 6S0 661 701 670 

I 12 '^ 3S2 531 623 655 659 639 672 

li8 " ...... 245 502 587 603 602 639 654. 

fOriginal 273 329 342 330 355 329 

I I month 242 302 339 339 336 341 

I Cement: j 3 months 247 294 302 307 324 340 

3 Standard < 6 •• 219 273 291 283 307 301 

Quartz Sand 9 204 253 293 2S4 301 294 

1 12 •• 167 241 259 243 281 292 

L18 ■• 132 187 231 232 245 263 

Eii-j. vilua based on o briqaettes only. 



ing is to lower the early strength and, if prolonged, the ultimate 
strength of the material. Cement, on standing, gradually ab- 
sorbs water and carbonic acid from the air, which first attacks 
the expansives such as free or loosely combined lime, then 
those ingredients that give the early strength, and lastly, those 
responsible for the final hardening. A certain amount of s:or- 
age. usually from, a week to a month, is necessary to obtain 
a sound cement. Further storage gives a cement of lower 
strength in the early stages of hardening, but affects the values 
at later periods but slightly, unless too much prolonged. When 
a cement contains a high proportion of sulphates, the falling 

*See Chapter X. 



TENSILE STRENGTH. 105 

off in early strength is more pronounced.* Material from one 
to three months old will usually give the best results in 
practice. 

Table XXVill. gives the results of a series of tests made 
by the author to demonstrate the effect of age on the strength 
of cement. The tests were made on a rotar\-kiln Portland 
from the Lehigh Valley district, which was about a month old 
when the first tests were made, and so was seasoned sufficient- 
ly to be entirely sound. The cement was kept in its canvas 
bag in the ordinary air of the laboratory, and at intervals tested 
with the results shown. 

Effect of Fineness. — The effect of increased fineness is, gen- 
erally speaking, to increase the strength of sand mortar, and 
to decrease that of neat cement. It seems natural that the 
finer a cement is ground the more readily it will be acted upon 
by water, hence becoming more effective, while the interior 
of the coarser particles remains practically inert. The finer 
cem^ent is, therefore, more active, and in a sand mortar will 
cover the surfaces of the sand grains more thoroughly, and 
thus will give higher values. The reason for the lower strength 
of neat briquettes is less apparent, but may be explained by 
the fact that the coarse particles give a coherence to the mass 
in furnishing something to which the finer particles can adhere, 
and that in breaking, rupture takes place around these parti- 
cles rather than through them, thus increasing the area of 
the breaking section, as is the case with sand briquettes. An- 
other possible reason may be that in the coarser cement the 
particles are better graded, and may pack more closely, thus 
giving a denser mass. 

It also follows that, because it is more readily acted upon 
by water, the finer cement will attain its ultimate or highest 
strength at an earlier period than the coarse one. 

The effect of fineness on tensile strength ma\ be clearly seen 
in Tables XXIX. and XXX. 

The fact that the coarse particles of cement remain iM-acti- 
cally inert, even after long periods of time, may be proven by 
regrinding old bri(|uettes and remoulding tliem, t^- b\- fasten- 
ing together with a rubber band the broken lialves o\ a neat 
briquette made from a coarse cement, in ritlier of which cases 
it will be found that considerable strength is developed. 

*See page 85. 



io6 



PRACTICAL C EM EXT TESTIXG. 









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TENSILE STRENGTH. 



107 



Effect of Environment. — The eiiA/ironment of the cement prior 
to testing exerts less influence on the strength than on the 
time of setting. High or low temperatures have little effect, 
provided the sample is brought to normal when the test is 
made. Excessive dampness is equivalent to a longer period of 
seasoning, provided it is not sufficient to cause actual hydra- 
tion. 

The temperature at which the briquettes are made exerts 
a somewhat greater influence, but for the ordinary ranges oc- 



TABLE XXX.— The Effect of Fineness on Tensile Strength of 

Portland Cement. 

(A Short Series of Tests by the Author.) 

TSTo TTnw Trfijii-Pfl P^^ Q^nt. ^Tensile Strength-> 

^^- Mow ireated of Water 7 days 28 days 

1. Neat cement 21.0 540 591 

2. Neat briquettes of material passing No. 200 sieve 22.0 481 502 

3. I — cement : i part standard quartz sand 12. i 479 653 

4. I — No. 2 material : i " " " " 12.4 456 683 

5. I — cement : 2 parts " " " 10.3 338 507 

6. I— No. 2 material : 2 " " " " 10.6 423 532 

7. I — cement : 3 " " " " 9-4 169 243 

8. I — No. 2 material 13" " " " 9.7 283 357 

9. I — cement : 3 " bar sand 9.6 120 163 

10. r — No. 2 material : 3 " " " 9.8 181 223 

(Cement in which the material retained on the 

(No. 200 sieve was replaced by sand of same size 17.6 493 557 

12. I — part No. II material : 3 parts standard 

quartz sand 9.0 164 235 

13. Cement passing No. 100 and retained on No. 200 

sieve . . 20.0 130 253 

14. Cement passing No. 50 and retained on No. 100 

sieve 16.0 . . 24 

Fineness of neat cement :— No. 50-0.0%; No. 100—9.2%; No. 200— 24.S".,. 
Each value average of 5 briquettes. 



curring in the laboratory the effect is practically neglig.ble. 
In regard to lower temperatures, Sabin''' says: "Jt appears 
that the briquettes made in a low temperature (34' to 37' V-^\\v.\ 
are usually stronger than those made in the ordinary tempera 
ture of 65° to 68° Fahr." The table of tests accomjianv ing 
this statement, however, shows the differences to be but slight 
and not altogether consistent. It is advisable, nevertheless, to 
keep the temperature of the laboratory as near 70" h'ahr. as 
practicable. 

♦In "Ceinenl and roiicrctc, " by L. V Sabiii. 



I08 PRACTICAL CEMENT TESTING. 

THE FORMING OF BRIQUETTES. 

Amount of Mixing Water.— Tables XXXI. and XXXIL show 
the effect of different percentages of mixing water on the ten- 
sile strength of neat and sand briquettes. For the ranges that 
are practicable for purposes of testing, it will be found that for 
early periods, dry briquettes give the higher values, but that 
ultimately the wetter mixtures generally equal and occasionally 
even exceed them. As stated in Chapter VIII., it has been 
shown that different cement mixtures have more nearly similar 
properties when mixed to the same degree of plasticity than 
when mixed with a fixed amount of water. The amount of 



TABLE XXXI.— Effect of Varying Percentages of Water on the Strength 

of Portland Cement. (Tests from paper on the '* Tensile Strength of 

Cement," by E. S. Lamed, Proc. Am. Soc. Test. Mats., 1903.) 

Sieve Test: « Wire: « Tpnsilft StrPnp+h 

Residue on Minutes ' 1 ensile btrengtn 



Brand -^j^^^^. ;^^ j^^ ^^_ tTa«^^ 24 7 28 3 6 12 

Percent. 50 100 180 ^^^'^^ ^^^^^ hours days days mos. mos. mos 



13 O.I 7.0 18.0 13 270 366 775 859 1067 892 832 

14 18 303 404 780 891 972 852 781 
16 22 327 363 602 725 844 806 723 
18 15 383 308 570 723 785 728 724 
20 56 703 225 590 718 760 674 636 
22 52 833 166 554 649 731 643 604 
24 188 918 42 510 691 695 632 574 

15 0.15 5.4 21.2 12 207 371 655 875 941 720 787 

16 29 297 303 750 973 1008 735 816 
18 80 355 260 649 773 831 645 748 
20 142 402 233 500 693 716 621 676 
22 268 473 184 546 635 658 601 589 
24 _ 327 912 167 539 649 644 629 755 

NOTE.— Each Value is Average of Six Briquettes. 



water required to bring different cements to the same consist- 
ency varies with the composition, age, fineness, etc., so 
that the proper amount must be determined experimentally in 
each case. Alethods for determining normal consistency have 
already been discussed,'^ and either a consistency obtained by 
the ball method, or that recommended by the Committee of 
the American Society of Civil Engineersf will give good results, 
although the former will be found somewhat easier to manipu- 
late. Whatever consistency be adopted, it is advisable to use the 
same for both time of setting and neat briquettes. The use of a 

*See page 93. 
tSee Appendix A. 



TENSILE STRENGTH. 1 09 

fixed percentage of water for all cements, such as is given in the 
specifications of the U. S. Army Engineers* is incorrect in theory 
and dif^cult in practice. The average Portland cement requires 
about 20% of water to bring it to the consistency required by 
the ball method, and about 21% for the Am. Soc. C. E. Com- 
mittee method. 

One great advantage in the use of wetter mixtures is that the 
moulds can be filled more uniformly by hand, since it is almost 
impossible to compact very dry briquettes similarly ; but, on the 
other hand, the wet briquettes are difificult to manipulate prop- 
erl}-, are liable to shrink in the m.oulds, and often contain large 



TABLE XXXII. — Effect of Variations in the Consistency of Mortar on the 

Strength of Portland Cement. 

(From Sabin's "Cement and Concrete.") 

Parts Sand to , Tensile Strength, Pounds per Square Inch, , 

1 Cement for Consistency Number 

by Weight 123456789 

o 608 635 763 744 708 707 729 685 

1 513 543 618 588 594 613 566 566 538 

2 429 ••• 447 398 393 382 

3 289 ... 322 329 310 ... 279 

5 208 ... 230 201 189 ... 167 

All Tests made at 3 Months. Sand— Crushed Quartz 

Consistency: ( 1.— Very Dry; Little or no Moisture Appeared 

I on Surface of Briquettes. 

Significance of Numbers: ^ 5.— About Proper Consistency for Briquettes. 
Increasing Per Cent. Water 9.- Very Moist; Mortar would barely Hold Shape, 
Used for Higher Numbers: I and Shrank in Moulds in Hardening, 



air bubbles which are responsible for low results. The normal 
consistency recommended gives neither the highest nor the most 
uniform values, but is an excellent mean between the two, and 
at the same time is most convenient for manipulation. 

In mixtures of cement and sand, the amount of water re- 
quired to produce normal consistency is much more difficult to 
obtain. It is practically im])ossil)le to determine its consistency 
by direct measurement, the mixture being too incoherent for 
the use of the ball method, and the sand grains not permitting 
of determinations l)y penetration. Since the practice of using 
a fixed percentage of water for any mixture is just as incorrect 
for sand mortars as for neat ])astes, although the effect is n^-it sc-* 
great, recourse must therefore be made to a formula by whicli 

•See Appendix I). 



no PRACTICAL CEMENT TESTING. 

the proper amount of water may be found, if the neat consistency 
has been determined. 

Several of these formulas have been proposed, although no 
one of them can be recognized as a standard. Feret's formulas 
are among the best known, and were evolved empirically from 
the plotting of curves representing the average judgment of 
several operators. These formulas are : 

For mortars of plastic consistency : 

E = — NA + 60 
3 

and for mortars of dry consistency : 

E = — NA + 45 

in which E = weight of water in grams required for one kilo- 
gram of dry mixture of cement and sand ; 

N = weight of water in grams required for one kilo- 
gram of neat cement; and 

A = weight in kilograms of cement in one kilogram 
of the dry mixture. 

The first formula gives the consistency generally used for 
hand mixing, while the second gives a consistency suitable for 
mechanical apparatus such as the Boehme hammer. While the 
first formula is well adapted for the average range of practice, 
it will be found that the extreme values are in considerable error. 
Moreover, it is impossible to vary the formula consistently for 
the use of different sands. 

The author has attempted to evolve a formula for the con- 
sistency of sand mortars from purely theoretical considerations 
but was unsuccessful, the great difificulty being due to the vary- 
ing void spaces in the different mixtures. However, by slightly 
altering the form and by introducing empirical constants, a 
'ormula was evolved which has given entire satisfaction in prac- 
tice for over three years. 

The formula is 

3 N + Sn + i 

4 (n + i) 

in which 

x=^per cent, of water for sand mixture; 



TENSILE STRENGTH. HI 

N =: predetermined percentage of water required to bring 
neat cement to normal consistency ; 

n = parts of sand to one of cement by weight ; 

S = a constant depending on character of sand and consist- 
ency desired. 

The empiric constants used in this formula were obtained from 
the results of almost 2,000 tests covering the greater part of one 
winter's experimental work. 

This formula has the advantages of being applicable to any 
mixture from i : i to i : 5, is adaptable to any sand, and may be 
altered to give any desired consistency. For ordinary processes 
of hand moulding, the constant S becomes 30 for standard 
quartz sand, making the formula read : 

• 3 (N + 10 n) + I 
4 (n + i) 

the values for which are given in Table XXXIII. 

For Ottawa sand, 8 = 25, while for the bar and bank sands 
ordinarily used in construction, S varies from about 27 to 33. 



TABLE XXXIII. 


— Percentages 


of Water 


to Use 


in Mixtures 


of Cement 




and Standard Quartz 


Sand- 


—Based on 


Formula, 3(N+10n) + l 
4(n + l) 




Neat 


1.1 


1-2 


1-3 


1:4 


1:5 


Neat 


1:1 


1:2 


1:3 


1:4 


1:5 


15 


9-5 


8.8 


8.S 


8.3 


8.2 


26 


13-6 


II. 6 


10.6 


lO.O 


95 


16 


9.9 


9.1 


«7 


8.S 


8-3 


27 


14.0 


II. 8 


10.8 


10. 1 


9.7 


17 


10.3 


9-3 


8.9 


8.6 


8.4 


28 


14.4 


12. 1 


10.9 


10.3 


9.8 


18 


10.6 


Q.6 


9.1 


8.8 


8.5 


29 


14.8 


12.3 


II. I 


10.4 


9-9 


19 


II. 


9.8 


9.3 


8.9 


8.7 


30 


151 


12.6 


II 3 


10.6 


10.0 


20 


11.4 


10. 1 


9-4 


9.1 


8.8 


31 


15-5 


12.8 


II 5 


10.7 


10.2 


21 


118 


10.3 


9.6 


9.2 


8.9 


32 


159 


13 I 


II. 7 


10. () 


10.3 


22 


12. 1 


10.6 


9.8 


9-4 


9.0 


33 


16.3 


133 


II. 9 


11. 


10.4 


23 


12.5 


10.8 


10. 


9-.S 


9.2 


34 


16.6 


i3<^ 


12. 1 


II. 2 


10.5 


24 


12.9 


II. I 


10.2 


9-7 


9-3 


35 


17.0 


T3-8 


12.3 


1 1-3 


10.7 


25 


133 


"•3 


10.4 


9.8 


94 


3^ 


17.4 


14.1 


12.4 


li-S 


10.8 



If it is desired to use a somewhat drier consistency ailaptablc 
for use with mechanical moulders, S may be reduced to 26 or 27 
for standard quartz, and to 21 or 22 for Ottawa sand, and it will 
be found that the consistencies obtained are practically uniform 
throughout the entire range as given in the table. Tn routine 
testing with standard quartz sand the values given in Tabic 
XXXIII. will be found convenient and satisfactory. 



112 PRACTICAL CEMENT TESTING. 

Temperature of Mixing Water.— For the orclinar\ ranges liable 
to occur in a laboratory, the temperature of the mixing water 
has little if any effect upon the strength. Extremely cold water, 
however, will retard the process of hardening, and hot water 
accelerate it, but it requires a very decided variation to affect 
the results appreciably. It is advisable, nevertheless, to insure 
against error by always using water as near to 70 degrees Fahr. 
as practicable. 

Purity of Mixing Water. — Small amounts of salts in solution 
or impurities in suspension generally have but little effect on the 
strength. Care, however, should be taken that the water is 
neither acid nor strongly alkaline. Water from the storage 
tanks is often very alkaline, and, if used in mixing, ma\ have an 
appreciable influence on the results. Sea-water should never 
be used in routine tests, although ]\I. AFexandre'^ states that 
there is little difference in the strength of mortars gaged with 
fresh and with salt water. Suspended mineral or organic matter 
In sufiflcient quantity may introduce errors of no small mag- 
nitude, especially in tests of sand mortar. 

Sand. — It Is scarcely within the province of this book to enter 
In detail into the effect of different varieties of sand on the 
strength of the resulting mortar. f It will be sufficient to state 
that ordinarily a rather coarse sand will give higher results than 
a finer one, and that a sand whose grains are graded in size will 
surpass either one, and furthermore that the differences In 
strength caused by the use of different grades of sand may 
amount to as much as 200 or 300 pounds. For purposes of 
routine laboratory testing therefore, it is necessary to employ a 
standard sand. If the results obtained in different laboratories 
are to be at all comparable. 

The sand commonly employed in the United States for cement 
testing Is artificially prepared crushed quartz, sifted to pass a 
sieve of 20 meshes to the lineal inch and to be retained on one 
of 30 meshes. The use of this sand was proposed In 1885 by 
the Committee of the American Society of Civil Engineers. As 
sold, the sand is never sifted clean, and therefore must either be 

♦Annalea des Fonts et Chaussees, 1890. 

tFor comprehensive data on the effect of the granulometric composition of 
eands on the strength of mortar, the reader is referred to "Cement and Con- 
crete," by L. C. Sabin; "Concrete— Plain and Reinforced," by F. W. Taylor 
and S. E. Thompson; "Cements, Mortars and Concretes," by M. S. Falk, and 
"Materials of Construction," by J. B. Johnson. 



TENSILE STRENGTH. II3 

sifted again in the laboratory, or else the sand as sold must be 
required to pass a limiting specification. It has been the author's 
practice to specify that not more than 3 per cent, of this sand 
shall either pass the No. 30 sieve or be retained on the Xo. 20, 
and then, if fulfilling these requirements, to use the sand as 
received without further sifting. 

Although, if sufficient care be exercised, this sand may be 
procured of very uniform character, there are nevertheless 
several serious objections to it — the angular character of the 
grains which make it difficult to compact the mortar closely, 
the high percentage of voids (40 to 45 per cent.), and the ex- 
pense and occasional difficulty of procuring it. 

For these reasons, the later Committee of the American 
Society of Civil Engineers has recommended the use of a 
natural sand from Ottawa, lUinois, sifted, as with the crushed 
quartz, to 20-30 size. This is a pure silicious sand, having grains 
almost spherical in shape, a void space of 30 to 35 per cent., 
and may easily be compacted into a dense mortar. Briquettes, 
broken at 7 and 28 days, made of one part cement to three parts 
of this sand will average from 20 to 30 per cent, higher than 
those made similarly from crushed quartz. If this sand is em- 
ployed therefore, the specification requirements for mortar 
briquettes should be increased by 20 or 25 per cent. Although 
Ottawa sand has several advantages over crushed quartz, its use 
at the time of this writing is by no means general, chiefly for the 
reason that the majority of the present data on cements, and also 
the greater number of existing specifications, are based upon 
results obtained with crushed quartz. 

For field laboratories situated in places where it is difficult 
and expensive to procure either of these sands, it is permissible 
to employ a local sand, which has first been carefull\ tested in 
comparison with the standard sand on which the si^ocifications 
are based. The sand should always be sifted to a definite size, 
preferably 20-30, since every natural sand wirics considerably in 
different parts of the bed. 

The sieves for sand testing should be carefully calibrated in a 
manner similar to those used for testing the fineness of eenient,* 
and the wire should be of the following sizes: No. JO. 0.0165 
inches; No. 30, 0.OTT2 inches. 

*See page 08. 



114 



PRACTICAL CEMENT TESTLYG. 



The standard sands of England, France and Germany are 
natural sands occurring in definite localities, and sifted to a size 
nearly equivalent to 20-30. In France a compound or graded 
sand is also employed in certain tests. German normal sand 
gives results averaging 5 or 10 per cent, stronger than crushed 
quartz. 

Form of Briquette. — The standard American form of tensile 
briquette is shown in Fig. 43. This form was adopted by the 
Committee of the American Society of Civil Engineers in 18S5, 
and endorsed by the later Committee except for the rounding 
off of the corners, which makes it more easy to fill, handle, and 



^ 



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k " /?/ " ^^ i 


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Fig. 43. — American Standard Form of Briquette. 

remove from the moulds. The standard English briquette* is 
practically identical. Each has a cross section of one square 
inch. The objections to this form of briquette are first, 
that the angle between the bearing surfaces is too small, 
thus inducing lateral compressive and cross-breaking strains ; 
secondly, that the reduction in area at the least section is in- 
sufficient, and also that the distance between the least section 
and the plane of the bearings is not great enough to ensure an 
equal distribution of stressf in the former. 

*See Fig. 140, Appendix E. 

"^For a mathpmatioal discussion of the distribution of stress over the least sec- 
tion of a briquette, see Johnson's "Materials of Construction," Chap. XXI. 



TENSILE STRENGTH. 



1^5 



The German standard briquette (Fig. 44), also adopted as the 
French standard, having an area of 5 square centimeters at the 
breaking section, is superior to the American form in the angle 
of the bearing surfaces, but, on the other hand, has too sharp a 
reduction of area at the least section, which, while it insures all 
breaks occurring in that place, makes the distribution of stress 
very unequal and hence gives lower values. The more clumsy 
shape is another factor in its disfavor. Comparative tests show 
that the American form of briquette gives results 10 to 20 per 
cent, higher than the German. 

While the defects of both of these briquettes are well recog- 




FiG. 44.— The Standard Form of Cement Briquette Used on 
the Continent of Europe. 

nized, it is doubtful whether they will be altered for some time 
to come, on account of the expense, difficulty and mnfusitui 
necessarily following such a change. 

Moulds. — Moulds for tensile briquettes are made almost uni- 
versally of brass. Cast iron is occasionally used, Init moulds of 
this material soon rust and become unfit for use. 

Moulds are made either single or in gangs of three, iom, tive, 
and even ten, but when over four or five are, however. imwicKly 
and expensive to handle and maintain. Gang moulds of three 
and four will be found to give the l)est results in practical work, 
and are the most economical. Single moulds are filled com- 



ii6 



PRACTICAL CEMEXT TESTLXG. 




parativcly slowly, even under the most expert manipulation, 
while larger gangs must either be very heavily made or else 
will soon spread m the center, thus destroying the accuracy of 

the cross-section. Larg^e g^ang^s 
are usually provided with one 
or more clamps or bolts in the 
middle, but these require time 
to manipulate and make the 
mould awkward to handle. A 
plain mould ^i i^is. wide in gangs of three or four will main- 
tain its shape without spreading for several years. To give ad- 
ditional rigidity, the sides of the moulds are sometimes channel 
shaped, and although wider and hence stifi'er are somewhat 
lighter. The additional width, however, makes handling the 
mould more awkward, and, for routine work, it is beHeved that 
little is gained by their use. 
The clamps holding the two parts of the mould together are of 



Fig. 45. — Briquette Moulds. 




Fig. 46. — Type of Briquette Mould Recommended by the A. S. C. E. Committee 



several forms. The screw clamp shown in Fig. 45 admits of 
greater rigidity, but is very clumsy in manipulation and requires 
unnecessary space in the damp closet. The end clamp used in 
the form of mould recommended by the Committee of the Amer- 
ican Society of Civil Engineers (Fig. 46) is simple and very con- 
venient. Fig. 47 shows another form of end clamp which is 
neither as simple nor as easily operated as that of Fig. 46. When 
end clamps are used, they should always be fastened to the same 
hall" of the mould as in Fig. 46 and never opposite each other 
like those of Fig. 47. The two halves of the moulds are either 
hinged together at one end, or made separately and fitted to- 
gether over dowel pins. Either type may be used for single 
moulds, but the halves should always be separate in gangs. 
After much experimenting the author has adopted the use of 



TENSILE STRENGTH. U^ 

the form of mould shown in Fig. 46 made in gangs of three and 
four. In fining and turning over, there are no clamps to get in 
the way, and in placing them in the damp closet, they can be 
packed very closely together and can be stood on their sides. 
In removing the briquettes, the moulds are placed side by side 
and the clamps all loosened together by two or three blows with 
a flat iron bar. 

They are cleaned by first scraping the sides with a six inch 
pointing trowel ; the halves are then separated and placed side 
by side along a table, the briquette holes forming long grooves 
along the line. The inner surfaces are then cleaned all at once 
by first scraping them with an iron bristle brush of the kind 
called a "sink scrub brush," and then by rubbing with a piece 
of oily w^aste. Every other half is then placed on its mate, and 
the clamps fastened by knocking them down with the iron bar 



Fig. 47. — Another Form of Briquette Mould. 

previously described. The moulds used for making 200 
briquettes may by this method be cleaned by one man in about 
half an hour. The life of a 3 or 4 gang mould used dailv in 
this manner is about 2 or 3 years. 

Methods of Mixing and Moulding. — In the uniform mixin;; and 
moulding of cement bricjucctis is encountered the greatest dif- 
ficulty in the testing of cement, primarily on account of the 
great influence of the factor of personal e(|uation. It is im- 
possible to describe on paper a method by which al)solutely 
uniform results may be obtained unless such elal)oratc ap- 
paratus is employed that the metliod becomes imjiracticablo for 
the ordinary laboratory. At best, therefore. an\ liand method 
produces results that are com|)arative among themselves rather 
than absolute. 

The first attempt in this country to j)rescril)e a uniform method 



Il8 PRACTICAL CEMENT TESTING. 

for making briquettes was made by the Committee of the Amer- 
ican Society of Civil Engineers in 1885, and was as follows : 

"The proportions of cement, sand and water should be care- 
fully determined by weight, the sand and cement mixed dry, and 
the water added all at once. The mixing must be rapid and 
thorough, and the mortar, which should be stiff and plastic, 
should be firmly pressed into the moulds with a trowel, with- 
out ramming, and struck off level." 

On account of the many obvious ambiguities in these rules, 
the later Committee in 1903 recommended the following 
method,* which is practically an elaboration of the preceding: 

"The material is w^eighed and placed on the mixing table, and 
a crater formed in the center, into which the proper percentagef 
of clean water is poured ; the material on the outer edge is 
turned into the crater by the aid of a trowel. As soon as the 
water has been absorbed, which should not require more than 
■one minute, the operation is completed by vigorously kneading 
with the hands for an additional i^ minutes, the process being 
similar to that used in kneading dough. A sand glass affords 
a convenient guide for the time of kneading. During the opera- 
tion of mixing, the hands should be protected by gloves, prefer- 
ably of rubber." 

"The moulds should be filled at once, the material pressed in 
firmly with the fingers and smoothed off wdth a trowel, without 
ramming; the material should be heaped up on the upper sur- 
face of the mould, and in smoothing off, the trowel should be 
drawn over the mould in such a manner as to exert a moderate 
pressure on the excess material. The mould should be turned 
over and the operation repeated." 

A method employed by several laboratories for mixing is, 
after the water has been added and absorbed and the materials 
formed into a pile, to take a large trowel and starting from the 
edge to w'ork through the pile, scraping it down little by little 
with the edge of the trowel under slight pressure. This, how^- 
ever, requires the expenditure of considerable time (to reach 
the same degree of plasticity about twice as long as the knead- 
ing method), and experiments by the author have shown it to be 
productive of less uniform and accurate results. For very quick 
setting cements the method is almost impossible. 

*See Appendix A. 
tSee page 93. 



TENSILE STRENGTH. 119 

]\Ir. Sabin"^ recommends for mixing the use of an iron box 
with a sloping bottom, in which the mortar is worked with a 
hoe. 'The box is 2 feet 7^ inches long, 6 inches wide at the 
bottom, and at the center is 6 inches deep. The level part of the 
bottom is 3 inches by 6 inches, and from this level part the in- 
clined portions of the bottom slope up toward the ends at an 
inclination of about 22^ degrees. The sides of the box extend 
below these inclined planes to give a level bearing for the box 
when in use. It is also well to have the sides flare enough to 
give a width of 6J inches at the top to prevent the hoe from 
becoming wedged. A 'German clod hoe,' which is strong and 
heavy, yet a trifle flexible in the blade, is used in connection 
with the box." 

''The weighed quantities of the dry ingredients being put in 
the box and well mixed, the measured volume of water is 
added. Two minutes of hard work, in which the operator may 
put all his strength, is sufficient to bring the mass to plasticity 
if the amount of water added is correct." 

The author has experimented with this box at some length 
and found it crude, tedious, awkward, and no better than hand 
methods in regard to the elimination of personal equation, 
although J\Ir. Sabin says "A return to the trowel and slab method 
of mixing is not likely after a trial of this simple device." It is 
improbable, however, that a device of this sort would ever take 
the place of the simple and effective hand methods generally in 
vogue. 

The standard methods of the United States Army,t follownig 
German practice, recommend filling the moulds by tamping 
with a hammer. It is not believed, however, that tanii)ing 
methods, unless mechanical, secure any greater uniformity of 
results than compacting under hand pressure, and the tibjeclion 
of the time required for this process is a serious one. iMJlng 
bri(iuette moulds under blows from a hammer is a verv un- 
common practice in this countrw 

Many other methods of hand mixing and moulding are em- 
ployed here and there, but none have any recognized status. 
The trend seems to be more and more to adapt tlie hand knead- 
ing process, and in following the c^nly recngni/.ed standard 

•In "Cement and Concrete." by L. C. Sabin. p. 1<><» 
tProfeasional papers No. 28, Corpa of Engineers. U. S. Army. 



120 



PRACTICAL CEMENT TESTING. 



method of the United States, to arrive at greater uniformity both 
in methods and results. 

The Author's Method. — The method outhned by the recent 
Committee of the American Society of Civil Engineers has been 
used by the author for several years except that a slightly drier 
consistenc> (determined by the "ball" method) is taken, and the 
mixing is only continued for one, instead of i J minutes, and after 
repeatedly experimenting with many other methods and varia- 
tions, this method has been found to be the most efficient in 
routine work. It is not claimed that different operators in dif- 
ferent laboratories can obtain even substantially similar results, 
but a single operator, or several working together can, when 




Fig. 48. — Scales for Cement. 

employing this method, soon duplicate their results with consid- 
erable accuracy, and can day after day make uniform and accur- 
ate tests. The speed of making briquettes in this manner is 
probably greater than m any other, which is a most important 
consideration in routine work. 

On a scale (Fig. 48), sensible to -J a gram, are first weighed 
1,000 grams of the ingredients, this quantity being just suffi- 
cient to make eight briquettes, and a convenient amount to ma- 
nipulate. The cement is formed into a crater and the pre-de- 
termined quantity of water poured into the center. The author 
employs the normal consistency as obtained by the ball meth- 
od,* after one minute of kneading. It is essential that the 
kneading be always continued for a definite time, since the plas- 

*See page 93. 



TENSILE STRENGTH. 



121 



ticity of the paste increases with the time of working-, and it is 
believed that one minute of hard working is amply sufficient to 
obtain a uniform mixture. 

When sand mortars are gauged, the cement and sand are 
first thoroughly mixed dry (Fig. 49), by hand and trowel, until 
the pile is of a uniform color, then formed into- a crater, and 
the amount of water given in Table XXXIII. ,f poured into the 
center (Fig. 50). Material from the edge of the crater is turned 
into the center until the water is all absorbed, then the mixture 
is turned over loosely with the trowel two or three times to dis- 




FiG. 49. — Making Briquettes— Mix"ing the Dry Ingredients. 

tribute the wetted portions evenly, and finally formed into a 
rounded pile ready for kneading. A six-inch "ix^intin^ trowel" 
is the best form for mixing. 

The proper kneading of tlic mixture is extremely ditlicult to 
describe and yet is essential for correct m:l^il^nl;ui^n. 1.000 
grams of material, after the water is added and absnrl)etl. form 
a pile which can just be comfortably coverc^l willi the two 
hands. The kneading is performed h\ placing the lingers 
across the pile and pushing the base of tlie band towards iheni 
while exerting a downward pressure (I'ig. 51). A lair idea of 
the motion mav be obtained if the reader will plac<> '^-^ ^aiuls 



tSefi page 111. 



122 



PRACTICAL CEMENT TESTING. 



on a table, arched so that only the ends of the fingers and the 
base of the hands by the wrists are touching, the thumbs of¥ the 
table and crossed on each other above the back of the hands 
and the forefingers almost in contact, and then, without mov- 
ing the fingers, push the wrists quickly towards them, pressing 




Fig. 50.— Making Briquettes— Adding the Water. 




Fig. 51. — Making Briquettes— Kneading. 

down at the same time. The movement of the wrists is re- 
peated five or six times without changing the position of the 
fingers ; then the pile, which is now spread in a line across the 
direction of working is rounded, turned through 90°, and the 



TENSILE STRENGTH. 



123 



kneading repeated. The pile should be worked, rounded and 
turned about sixteen times in a minute. The downward pres- 
sure exerted should be about 10 or 15 pounds. 

In filling the moulds enough material to about half fill them 




Fig. 52.— Making Briquettes— Filling the Mould. 




Fig. 53. — Making Briquettes - Compacting the Mortar. 

is first introduced and distributed evcnl\ o\cv the bottom with 
the fingers and thuml)S (Fig. 52), but willunit oxorling any ajv 
prcciablc pressure; this will be found necessary to make the 
mass of the briquette homogeneous. An excess oi material 



124 



PRACTICAL CEMENT TESTING. 



is then placed in and on the mould, extending about half an inch 
above it, and pressed in firmly with the thumbs, without ram- 
ming. In filling a gang mould it is turned to point away from 
the operator, and then starting from the far end pressed with 
both thumbs (Fig. 53), 3 times in each briquette, once in each 
head and once in middle. The pressure exerted should be 
about 25 to 3c pounds. The mould is then turned back through 
90°, an excess of material again placed on top, over which a 
trowel is drawn several times under a pressure of about 5 
pounds, each time cutting of¥ more and more of the excess ma- 
terial until it is flush with the surface of the mould (Fig. 54). 




Fig. 54. — Making Briquettes — Troweling the Surface. 

The material remaining on the sides of the top is then scraped 
off wdth the edge of the trowel, and the briquettes smoothed 
with two or three more strokes. 

The mould is then lifted from the table with a sliding mo- 
tion, turned over, an excess of material placed on the original 
bottom, now the top, and surfaced with the trowel as before. 
The moulds containing neat briquettes, after being surfaced on 
the first side, and lifted from the table, are placed on strips of 
glass 4 inches wide, J-inch thick, and of a length suited to the 
racks in the damp closet,* and are surfaced for the second time 
on these strips of glass, which are then placed in the damp 
closet. The moulds containing briquettes of sand mortar arc 

♦See page 131. 



TENSILE STRENGTH. 



12: 



surfaced both times on the mixing table and then placed in the 
closet on their sides. It is advisable to leave the briquettes in 
the moulds during the entire time they are in the damp closet, 
but, if necessary, they may be removed as soon as thoroughly 
hardened. 

The mixing of cement pastes and mortars should always be 
performed upon a slab of glass, slate or other non-absorbing 
surface ; glass will generally be found the most satisfactory on 
account of the ease of keeping it clean. A convenient mixing 



[Waste/^Can\ 



Cxilv. Iron 



J8xUM 
Class 



24x1x48" Soap Stone 



, iSheefofFelt 
-^^ -jOlass :l"Board 




Plan.. 
Soap Sfone--^ 



.■■/"Board Top 



V- -5x J' 



-3W- 



^tTt 



u \ 

End Elevation, Side Elevation. 

Fig. 55. — Sketch of Mixing Table Used in the Philadelphia Laboratories. 

table for laboratory use is shown in Fig. 55, the mixing slab 
being of glass, and the top of the larger part of soa])stonc. A 
mixing slab may be placed on each end, if the volume of work 
requires the constant services of two operators, h^or small 
laboratories a plate of glass, two feet S(|uaro and "I -in. thick, 
fastened on an ordinary table is sufficient. 

The hands should always be i)rotecte(l by rubber gloves, when 
mixing cement, or the lime contained in it will, after a time, 
make them extremely sore ; and the j^aste also will get under the 
finger nails, from which it is often very difficult to remove. 



126 



PRACTICAL CEMENT TESTING. 



Mechanical Mixing and Moulding. — IMany devices for the 
mechanical mixing and moulding of briquettes have been pro- 
posed, among the simplest of which may be 
mentioned ice cream freezers, milk-shake ap- 
paratus, and sausage choppers, all of which 
have been tried for mixers, while many 
forms of presses and tamping devices have 
been employed in forming briquettes. 

One of the first of the mixing machines 
( Fig. 56) was designed by Henry Faija and 
consists of a pair of paddles revolving in the 
mixing pan. The author has modified this machine (Fig. 57), 
adapting it to practical use in enclosing the gearing, thus pre- 




FiG. 56. — Faija's Mortar 
Mixing Machine. 




Fig. 57. — Improved Form of Mortar Mixer Designed by the Author. 

venting it from becoming clogged, and in making the mixing 
pan removable, thus much simplifying the cleaning of the pan 
and paddles, which are brushed down with a bristle brush. The 
materials are placed in the pan, attached to the machine, turned 
20 times dry, then water inserted through a funnel and turned 
40 times. The mixing is very complete, but there is little of the 
working of the mortar necessary to the production of good 
results. 

Steinbruch's mortar machine (Fig. 58) is effective in working 
the mortar, which is accomplished by means of a wheel revolv- 
ing in a groove in the pan under which the material is forced 
by means of blades. A disadvantage of this machine, however. 



TENSILE STRENGTH. 



127 



is that the materials must first be hand mixed before being in- 
troduced. A combination of this machine with the preceding 
would give excellent and uniform results, if time could be af- 
forded for so elab- 

r~^ °^^^^ ^ process. 

J — J — ri k-J^ Of the briquette 

forming machines, 
that shown in Fig. 
59j an American 
adaptation of the 
German Boehme 
hammer, is one of 
the best known. In 
this device, a ham- 
mer of fixed weight 
is made to fall on a 
disc placed over the 
mould containing 
the briquette. The number of strokes per minute is fixed, and the 
machine is automaticall}/ stopped at the end of a definite number 
of blows. The machine is also made in batteries of two, three 
or four hammers for the simultaneous treatment of several 
briquettes. 

Another simple device on the lines of a stamp mill and on the 
principle of the hammer form is shown in Fig. 60. The material 




Fig. 58. — Steinbruch's Machine for Working 
Cement Mortars. 




Fig. 59.— Briquette Machine of the Hammer Type. 

is placed in a double mould, the upper being used as a guide and 
to hold the excess material, and given a fixed number of bUnvs. 



128 



PRACTICAL CEMEXT TESTIXG. 




^Machines for compacting briquettes under static load arc also 
employed. That shown in Fig. 6i, by turning the crank, applies 
a static load of either 250, 500, 750 or 1,000 pounds. When the 
desired load is reached, a clutch is automatically released and a 

second eng^aged which releases 
the load, although the crank is 
turned in but one direction 
throug-hout the entire opera- 
tion. Another machine of 
4,000 pounds capacity is illus- 
trated in Fig". 62, in which the 
load is applied and released 
by the hand w^heel, and its 
amount indicated on the 
spring dial. 

The author has experi- 
mented at some length on 
these different mixing and 
Fig. 60. — Briquette Machine of the Stamp moulding machines, and 
Mill Type. found that none of them is 

adapted to the requirements of routine testing. They require 
much more time to operate, and at best give results that are but 
a very slight improvement in uniformity over ordinary hand 
methods. Briquette formers operating under static load are ex- 
tremely unsatisfactory, it being im- 
possible to prepare a briquette of uni- 
form density even under a load of 
4,000 pounds unless made very wet, 
in which case great difficulty is expe- 
rienced in removing them from the 
machine. Hammer formers give bet- 
ter results, but are even slower to 
operate and are entirely impracti- 
cable where many tests are to be 
made unless several extra men are 
employed for operating these ma- 
chines alone. ^loreover, the author's 
tests on the best of these machines 
gave a probable error in the results Fig. 61. -Machine for Forming 
of 3% against only 4% for hand Briquettes Under Static Load. 



/ 


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"01 




F^ 


\\"^ 




P'^ 


r 


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L 




^^2i»^^ 





TENSILE STRENGTH. 



T29 



methods, so that the increased accuracy is disproportionate 
to the time expended. In routine testing, therefore, these ma- 
chines have no place. In experimental work, however, they mav 




Fig. 62. — Machine for Forming Briquettes Under Static Load. 

be employed to advantage, a combination of the modified Faija 
mixer, the Steinbruch worker, and the hammer former giving 
the most uniform results. Figure 63 shows a battery of this 
apparatus as used in the Royal Testing Station at Berlin. 




Fig. 63.— a Battery of Mechanical Briquette Formers in the Koyal Testing 
Laboratory at Berlin, Gt-rniany. 



130 PRACTICAL CEMEXT TESTIXG. 

STORAGE OF BRIQUETTES. 

Environment During Setting. — It is common practice to place 
the cement briquettes, immediately after making, in a damp at- 
mosphere and allow them to remain there for 24 hours. The 
purpose of this procedure is twofold : — first, to insure greater 
uniformity, and second to prevent the briquettes, especially those 
made from neat cement, from drying out too quickh and thus 
developing shrinkage cracks, thereby greatly lowering the 
strength. Uniformity is gained by reason of the fact that all the 
specimens acquire their set under precisely similar conditions of 
humiditv. which cannot be controlled in the outer air. and which 



TABLE XXXIV. — Showing the Effect of Variations in the Time of Storage 

in Damp Closet en the Strength of A'ati^rai Cement. 

(From- Sabin's "Cement and Concrete.") 

Parts Crushed Age in t^ ,;i„ c» .\, t v, o t v 

-R..,.,-^ Quartz. 20-30 Davs. 

^•^^^•l to when 

1 Cement Broken 

A o 7 

I 7 

28 

1 28 

2 28 
B o 7 

28 

1 7 
I 28 

3 2S 

Each Result is Mean of 10 Tests. 

2s GTE. —Although these tests are made on natural cement alone, the action 
is typical of both Portland and natural cements.— The Author. 

has been shown to have a great influence on the setting and 
hence early strength of the cement. Small ranges of tem- 
perature in the damp closet seem to affect :he strength but little, 
but endeavor should be made to maintain an even temperature 
of as near 70" Fahr. as practicable. 

The eftect of duration of this treatment is shown in Table 
XXXR'., and generally is to increase the strength of the 
briquettes tested for short periods, especially those of neat ce- 
ment ; the difference, however, is slight and disappears after 2 
or 3 months. The standard time for storage in damp closets 
has been fixed at 24 hours, largely as a matter of convenience. 

















Hours in 


Moist Air Before 


Immersion 




8 


12 


24 


i8 


72 


168 


12-, 




139 


151 


161 


237 


QI 




106 


114 


114 


182 


IIO 




106 


IC9 


89 


113 


142 




i3« 


139 


152 


175 


102 




105 


112 


113 


IIS 




168 


iSi 


194 


185 


238 




200 


210 


224 


241 


243 




108 


137 


141 


157 


i6c 




27S 


283 


297 


297 


301 




120 


130 


137 


139 


152 



TENSILE STRENGTH. 



131 



The author has, however, shortened this time to 21 hours, the 
briquettes being made from 11 to i o'clock every day, and re- 
moved from the damp closet at 9 o'clock the following morn- 
ing, thus giving time to mark the briquettes and clean the moulds 
before the briquettes for that day are ready to be made. The 
24 hour neat briquettes are replaced in the damp closet for 3 
hours. 

Figure 64 is a sketch drawing of the damp closet used in the 
author's laboratory. It is made of ij-in. soapstone, except the 




Fig. 64. — Sketch of Damp Closet Used in the Philadelphia Laboratories. 

doors, which are of wood covered with zinc, and is made in 
two sections for the reason that it was found that il the hci^lu 01" 
the closet was excessive the humidity varied considerablx be- 
tween bottom and top. On the sides of each closet are fasiened 
cleats, on the upper two of which rest the glass strips on which 
the neat bricjucttes are made, whik^ the lowest pair of ek'ats sup- 
ports a wooden rack, on which tlie moulds ctitUaining >>;ind 
l)ri(|uettcs are placed on their sides. 1'he water is placed in the 
bottom part of each section, i^acli section will acc»>nnnodaie 
64 neat and 96 sand l)ri(|nettes, and as nian\ sections nse«l as the 



132 



PRACTICAL CEMENT TESTING. 



TABLE 


XXXV 


— Comparison 


of the 


Strength of Portland 


Cement 


When 








Kept 


n Air and in Water. 










(From a Large N 


umber of Tests by the Author. ) 












-Tensile Strength, Lbs. per Square I 


QCh 












Kept in 


Mixture 


24: 


7 


28 


2 


3 


4 


6 


1 






hours 


days 


days 


mos. 


mos. 


mos. 


mos. 


year 




r 


Neat 


417 


715 


767 


757 


741 


731 


758 


768 








: I 


361 


593 


692 


690 


680 


679 


684 


696 


Water \ 




: 2 


216 


370 


458 


459 


456 


456 


459 


462 




■ 3 


105 


210 


302 


309 


310 


312 


310 


309 


L 




: 4 


62 


131 


212 


229 


233 


232 


235 


234 




5 


38 


82 


154 


186 


196 


198 


195 


198 


r 


Neat 


400 


742 


793 


771 


740 


723 


722 


694 


1 




I 


349 


625 


702 


696 


690 


694 


692 


690 


Air { 




2 


220 


412 


481 


483 


462 


469 


460 


423 




3 


lOI 


239 


357 


342 


363 


360 


371 


352 


1 




4 


65 


153 


237 


275 


274 


270 


251 


279 


L 


I : 5 


46 


1-4 


206 


249 


252 


237 


237 


239 


TABLE XXXVL— 


Showing 


the Relation Between 


the Strengths 


of 






Briquettes Kept in 


Air and in 


Water. 








(From Falk 


's " Cements, 


Mortars and Concretes. 


") 










T 


ensile Strength in Lbs. per Square Ii 


„!, 








J. 






Age 




Neat Cement 




L Cement : 3 Sand 


1 Cement : 


5 Sand 






Water 


Air 




Water 


Air 




Water 


Air 


7 days. . 




658 
697 
814 


642 

651 
600 




277 
350 
457 
487 


301 
438 
538 
605 




127 
180 


131 

247 
335 
410 


/ '-^'^j -^ 

28 days 








84 days 








233 
281 


6 months . . 




638 






I year.. 






765 


575 




550 


703 




271 


442 


2 years. 






838 


507 




503 


650 




270 


408 


Gauged with 


23^ 




10.1% 




9.5% water 






Note.— Each Value Based on 5 or 6 Briquettes. 








TABLE 


XXXVIL— Effect of Temperature of Storage 


Water 


on the Tensile 






Strength 


of Natural Cement. 












(From 


Sabin's 


"Cement and Concrete.") 








Parts 


Age 

in 

Days 


, Tensile Strength, Pounds per 


Square Inch n 


No. Brand Sand to One 
of Cement. 




svhen Immersed in Water of Temperature 
of Degrees Fahr. 




by Weight 




380 


40° 50° 


550 


60° 


65° 70° 


80° 


I. A 







7 


146 


■•• 137 


125 




.. 126 


154 • 


2 









14 


144 


... 131 


125 


131 


[50 168 


208 


3 









28 


166 


... 178 




184 


.. 247 


280 


4 






I 


7 


83 


... 88 


'84 


89 


98 97 


121 


5 






I 


14 


84 


... Ill 




123 


150 


191 


6 






I 


28 


96 


... 156 


187 


... 221 243 


288 


7 









I 




143 ■ ■ • 


124 


120 


109 


109 


8 









7 




204 201 




183 


• • 193 


186 


9 






' 


14 




184 203 




204 


.. 229 


245 


10 









28 




221 245 




254 


.. 281 


303 


II 









60 




261 292 




348 


.. 382 


429 


12 


C 




I 


7 




134 140 




150 


.. 154 


158 


13 






I 


14 




149 162 




189 


.. 182 


216 


14 






I 


28 




198 223 




250 


.. 281 


296 


15 






I 


60 




251 286 




337 


.. 386 


403 


16 






3 


14 




50 58 




69 


.. 73 


100 


17 






3 


28 




67 87 




100 


. . 102 


157 


18 






3 


60 




104 127 




147 


.- 194 


231 


N"ote.- 


-The effect on the 


strength of Portland cement is 


similar, but not usually so 








well marked.— 


The Author. 











TENSILE STRENGTH. 1 33 

volume of work requires. The expense of this closet may be 
decreased by making it entirely of wood lined with zinc ; this will 
be quite good enough for any field laboratory, but will not give 
the satisfaction of the soapstone closet. 

A device employed in the temporary laboratory of the Atlantic 
Avenue Improvement of the Long Island Railroad was to utilize 
stationary laundr\ tubs simply by fastening cleats on the sides 
to hold the glass strips and, although somewhat inconvenient, 
this appeared to be entirely satisfactory as regards results. 

The use of some simple damp closet should always be required 
in even the most temporary of field laboratories. A damp cloth 
placed over the moulds may occasionally serve as a makeshift, 
but for regular work it is crude and inaccurate, unless given the 
most careful attention. If necessary to employ such a cloth, it 
should be so arranged that it never comes into contact with the 
briquettes and also that the ends of the cloth are placed in water, 
which prevents it from drying out quickly. 

Storage of Briquettes. — After briquettes have hardened 24 
hours in the damp closet, they are removed from the moulds and 
placed in water until ready for breaking. The chief reasons for 
storing in water rather than in air are that they are kept under 
conditions admitting of greater uniformitv and that the effect of 
the presence of injurious elements is more marked. Xeat 
briquettes kept in air generally are stronger in the early periods 
and weaker in the longer periods than those kept in water. 
Sand briquettes almost invariably are stronger in air (see Tables 
XXXV. and XXXVI.) 

The temperature of the water (Table XXXMT.) slightly 
afifects the strength of the briquettes, especially for the first pcricxi 
of 7 days. M. Alexandre'^ found that briquettes stored in water 
at normal temperatures gave higher values at 7 days than those 
at low temperatures, but that at 28 days the conditions were re- 
versed for neat briquettes, and the sand bric|uettes gave almost 
equal values, while after 3 months no differences were aj^parenl. 
The standard temperature is 70'^ Fahr. 

The water should never show an acid react ion. lu-i- be ex- 
tremely alkaline. The gradual solution of certain salts from tlio 
bri(|uettes soon makes the water stronglx alkaline, and hence 

*"Resea^che^^ Expcrlnicntalet^ Hur lo^» Mortlers llydniuliques."' 



134 



PRACTICAL CEMENT TESTING. 



should either be kept running or frequently changed.* If 
running water is used the flow should be extremely slow to pre- 
vent any possible washing action. It has been claimed that 
running water tends to produce low results after a year or two, 
but tests now over three years old made by the author have 
shown no appreciable difference between running w^ater and still 
water changed every two weeks. 

The design of the storage tanks used in the Philadelphia 



A Z,^x?x^ 




^^^:^^^^^^^^^^^fe^^^^^^?^5^^^s^ ^^^^^?^?^?^^^??^^ 



Front- Elevation. Side Elevation. 

Fig. 65. — Sketch of Storage Tanks Used in the Philadelphia Laboratories. 

Laboratories is shown in Fig. 65. They are made of i^-in. soap- 
stone supported on a steel frame work. Hot and cold water are 
fed through separate pipes controlled by valves to maintain a 
uniform temperature, and the rate of flow Is sufficient to change 
the water in each tank every hour. The capacity of each tank 
is about 1,400 briquettes, and the author has 12 of these in con- 

*Mr. Sabin in "Cement and Concrete" states that the difference in strength of 
neat and sand briauettes of natural cement kept in fresh and stale water may- 
amount to as much as 40 to GO per cent. 



TENSILE STRENGTH. 



135 




stant use. It has been suggested that baffle plates placed at In- 
tervals along the tank so arranged that the water flows over and 
under every alternate plate would be of advantage in preventing 

the water from flowing across 

the top of the tank without 
running around the briquettes, 
but a long series of tests made 
by the author on briquettes 
stored at the top and bot- 
tom of the tanks showed no 
appreciable difiference, thus 
proving such plates to be un- ^7 ^^ t^ r o • 

^ ^ ^ Fig. 66. —Pan for Storing Briquettes. 

necessary. 

A more economical construction of these tanks, suitable for a 
temporary laboratory, may be made by building them of wood 
covered with zinc. If running hot and cold water is not obtain- 
able the} may be filled with a hose ; a good method in this case 
is not to use the uppermost tank except for water, which is first 
fed into it, allowed to acquire the temperature of the room, and 
then fed to the briquettes below, thus avoiding any sudden 
chilling. For a still cheaper equipment, pans similar to those in 
Fig. 66 may be used. The water in these pans should be changed 
not less often than once a week, while larger tanks may be 
changed every two weeks. 

Briquettes should always be placed in the water on their sides, 
never flat, so that the water may more readily circulate around 
them. 

Marking Briquettes. — The author marks the briciuettes with 
their numbers by means of a soft lead pencil, when removing 
them from the moulds, these marks remaining ixM-fcclly legible 
for at least 5 years. 

Steel stamps are used in many laboratories, but it is necessary 
to place a thin strip of neat cement paste on the heat! of each 
mortar briquette to make the imj^rint visible. These stamps are 
applied immediately alter the ])ri(|uettos are made. Tliey rccjuire 
considerably more time for marking than the \c:u\ pencil, and 
their use has no apparent advantage. 



136 



PRACTICAL CEMENT TESTING. 



BREAKING THE BRIQIJETTES. 

Testing Machines. — For breaking the briquettes, machines are 
employed to apply the load and to measure the force necessary 
to cause rupture. Exclusive of the form and arrangement of 
the clips holding the briquettes, the requisites for a good machine 
are that it shall apply the load at a uniform rate starting from 
zero, that it shall be so arranged that the introduction of a sys- 
tematic error is impossible, 
and that it shall be adapt- 
able to rapid and at the 
same time accurate manip- 
ulation. The common types 
of these machines used in 
the United States may be 
divided into three classes : 
long lever, shot and spring 
balance. The long lever 
machines are probably the 
most accurate ; the shot 
machines have the ad- 
vantage of compact- 
^^ ness and of operating 
J vv^ithout needing con- 
stant attention and 
hence are the most 
speedy; the spring bal- 
ance machines are nei- 
ther particularly rapid 
nor accurate, but are the cheapest and probably best suited to the 
engineer, who makes but a few tests at infrequent intervals. 

The Olsen and Riehle standard machines are the most gen- 
erally used of the long lever types. Figure 6y shows the Olsen 
hand power machine. The load is applied by means of a hand- 
wheel and lever, while the poise, moved by means of a hand- 
wheel and cord, registers the amount of stress applied. This 
design has many disadvantages, chief of which are that the stress 
is not uniformly applied, and second that the cord moving the 
poise is not in line with the knife edge of the beam and hence 




Fig. 67. 



-The Olsen Hand Cement Testing 
Machine. 



TENSILE STRENGTH. 



137 



tends to pull it down, thus introducing a systematic error of no 
small magnitude. These objections have in a large measure 
"been overcome in the power machine, shown in Fig. 68. In this 
arrangement the poise is mechanically driven along the beam at 
a uniform rate, while the beam is balanced by the wheel in the 
center of the frame which applies the load, and which can be 
operated by hand or by power, preferably the former. When 
the briquette ruptures, an electric contact is broken, stopping 
the poise instantly. By means of the step pulley the load may 
be applied at six different rates 
of speed. 

The Riehle power machine 
( Fig. 69 ) is built on lines 
somewhat similar to the 
Olsen, and is described by the 
makers as follows : "This ma- 
chine is arranged for the stress 
to be applied to the specimen 
through belt and pulley, also 
by hand. Three speeds are 
obtained by shifting the belt 
on the cone pulley. A clutch 
controlled by the small handle 
starts and stops the movement 
of the screw ; thus the belt can 
be run continuously. After the 
briquette is placed in position, 
this clutch is engaged and the 
screw applies the stress to the 
specimen. When the briquette 
breaks, the clutch is thrown out and the screw returned cjuickly 
to its original position by means of the hand- wheel under the 
clutch. The full capacity of the machine is registered on the 
beam, and no end weights or readjustment of the poise is neces- 
sary. The poise is operated by the hand-wheel near the beam; 
it is propelled by means of a screw and registers down to i'>ne 
pound. After the poise is moved out and the test completed, a 
lever which disengages the nut from tlie screw ]HTmits the 
operator to move the poise back to zero instantl> ." 




Fig. 68.— The Olsen Power-Driven Ce- 
ment Testing Machine. 



138 



PRACTICAL CEMENT TESTING. 



Both of these machines are buih of a capacity of 2,000 lbs., 
and both have attachments for making compression and trans- 
verse tests. The Richie is also adapted for testing in torsion. 
While the general type of these two machines is very similar, it 
will be noticed that in the operation there is a radical difference 
in that the Olsen moves the poise at a uniform rate and balances 
it by hand application of the load, while the Riehle runs the 
screw applying the load at a uniform rate, and balances the 
poise by hand. Since there necessarily is, in a geared ma- 




69. — The Riehle Cement Testing Machine. 



chine, considerable lost motion, and also on account of lost 
motion in the clips, especiall> when rubber surfaces are used, it 
will be found that although the belt running to the machine 
moves at a uniform speed, the stress applied by the latter method 
is not uniform, but that the rate increases with the stress, so that 
theoretically the former method is better. On the other hand, 
however, it is extremely difficult to apply the load in the Olsen 
machine at an absolutely uniform rate, especially in high testing 
briquettes, there being usually a more or less jerking motion 
which destroys the absolute continuity of the rate of stress. In 



TENSILE STRENGTH. 



139 



practice, therefore, there is but httle difference in the accuracy 
obtained, or in the efficiency of these two forms. 

Since these long lever machines require power to operate them 
to the best advantage, occupy considerable space, and require 
more constant attention as well as some skill, a demand was 
created for a simple, automatic, compact device, requiring no 
power and little skill to manipulate. These conditions have been 
met in the "shot machines," of which the Fairbanks (Fig. 70) 
is the oldest and best known. The construction can be seen at 
once from the figure, and needs no further explanation. The 

method of operation given 
in the manufacturers' cata- 
logue is as follows : 

" Hang the cup F on the 
end of the beam D. See 
that the poise R is at the 
zero mark and balance the 
beam by turning the l:)all 
L. Fill the hopper B with 
fine shot. Place the bri- 
quette in the clamps N-N, 
using great care to 
avoid eccentric- 
ity. Tighten the 
hand-wheel P suffic- 
iently to cause the 
Fig. 70 -The Fairbanks Testing Machine. graduated beam D to 

rise to the stop K. Only enough pressure should be exe![cd to 
hold the beam firmly against the stop, not enough to transmit 
any strain to the specimen. Open the automatic valve J, so as 
to allow the shot to run into the cup F. At the point where the 
spout joins the reservoir will be noticed a small valve, bv whicli 
the flow of shot may be regulated." 

"When the briquette breaks, the l)oam D will drop and auto- 
matically close the valve J. Certain cements strc-tch or give to 
such an extent as to allow the beam to strike the valve before 
the specimen breaks. If this should occur, carelully raise the 
end of the beam with one hand until it again touches the stop k ; 
with the other hand gently tighten the hand-wheel sufficiently to 
hold the beam in place, and again allow tlir shot to run. I'nder 




140 PRACTICAL CEMENT TESTLVG. 

no circumstances should the wheel be tightened before the 
beam has been lifted against the stop, as such action invariably 
causes the specimen to break, rendering an accurate test im- 
possible." 

"After the specimen has broken, remove the cup, with its con- 
tents, hanging the counterpoise G in its place. Hang the cup F 
on the hook under the large ball E, and weigh the shot, using 
the poise R on the graduated beam D and the weights H on the 
counterpoise G. The result will show the number of pounds re- 
quired to break the specimen." 

The catalogue then goes on to say : 'Tt has several times come 
to our notice that many users of these machines have been in the 
habit of applying an arbitrary strain by means of the hand- 
wheel, adding this strain to the actual result obtained in the 
proper manner. As one young man expressed it : *We apply 
pressure with the hand-wheel equal to about four hundred 
pounds, as the other way is so slow.' This is so obviously un- 
fair as to need no comment." 

In spite of this assertion, however, the author believes the 
"young man" is in the right, for the reason that in following the 
method of the catalogue, the raising of the shot bucket entirely 
releases the load and brings the stress to zero, then suddenly 
applies the whole load again and increases it to the point of 
rupture, thus entirely destroying the continuity of the increase 
in stress. ]\Ioreover, this readjustment must take place when the 
briquette has nearly reached its ultimate strength, and even if 
the bucket is let down slowly, the sudden application of the load 
is liable to cause premature failure, so that evidently it is more 
accurate to apply an initial load of 200 or 300 pounds than to 
make this readjustment, which is exactly equivalent to applying 
an initial load of over 500 pounds. The proper method of 
operating this type of machine therefore is to apply such an 
initial load that on rupture the graduated lever will have 
lowered to a horizontal position, and is almost touching the 
valve. 

This method, however, requires much experience and also a 
knowledge of about what value to expect from each briquette, 
so that even under the most favorable conditions it is not cap- 
able of precise determinations. This serious objection of 



TENSILE STRENGTH. 



141 



necessary initial stress has been overcome in the "Improved 
Fairbanks" machine, shown in Fig. 71 described as follows: 

*'It is our regular cement testing machine equipped with a 
sub-base containing a worm and worm gear connected to an 
axis, which is threaded and passes up through the base and 
hand-wheel P into a block, and the latter connected to the loweV 
clamp. The gear is actuated by the worm, the end of which 
is fitted to receive a key crank, passing through the front of the 
sub-base. A hook lever Y 
on the right hand end of 
the sub-base serves to dis- 
engage the worm from the 
gear, then the hand-wheel 
P may be used for rapid 
adjustment in returning the 
clamps to position to re- 
ceive the next briquette." 

*' In operation, the bri- 
quette is placed in the 
clamps, and adjustment 
made by the hand-wheel 
P until the indicators are in 
line. By means of the hook 
lever Y the worm is now en- 
gaged with the gear. The 
shot valve is then opened, al- 
lowing the shot to run into 
the bucket, and the crank 
is turned with sufftcient 
speed to hold the beam in equilibrium until the hriiinotte is 

broken." 

A better method for practical oi)cration is lo adjusi iho lever 
as with the old machine to bear against the sloi> K, and ihen on 
those l)ri(|uettcs with which the lover drops ioo low, to engage 
the worm and float the lever with the crank. This niav not Ik- 
quite as accurate, but it avoids the constant aitontii^n oi the 
operator, thus giving him linu- to note the value of the preced- 
ing test, and to get the next hriiiuette ready, while the test is in 
progress, thus effecting great saving in the time of operation. 




Fig, 71. — Improved Form of l-airbanks 
Cement Tester. 



142 



PRACTICAL CEMENT TESTING. 



The only systematic error of any importance in the operation 
of this machine is due to the fact that after the rupture of the 
briquette a small amount of shot escapes from the valve before 
it can be closed, and also the shot falling through the air is 
weighed in the bucket, although not effective in producing rup- 
ture. The amount, however, is very small, may easily be deter- 
mined by experiment, and can be either applied as a correction^ 
or the beam so balanced that the error is compensated. 
The 'Talkenau-Sinclair" shot machine (Fig. '/2), sold by Olsen 

& Co., is similar in 
type to the Fairbanks, 
although operating 
somewhat differently. 
*"The load is applied 
through a system of 
levers by means of 
the weight shown on 
the extreme right. Be- 
fore starting a test this 
weight on the right 
is counterbalanced by 
shot held in the kettle 
on the left end of the 
same beam. To make 
the test the valve in 
the bottom of this 
kettle is opened, and 
as the shot escapes 
its equivalent of the 
weight on the right 
hand end of the beam acts on the briquette. The cut ofif of the 
shot is afifected by the upper grip striking the horizontal arm 
which extends just above it, and thus releasing the curved arm 
carried on the spindle immediately to the left, this curved arm 
in turn striking the valve and closing it. The small hand-wheel 
for adjusting the lower grip is arranged so that it will auto- 
matically slip on the adjusting screw as soon as a predetermined 
load has been applied to the briquette." 
The shot is weighed on a spring balance so graduated that the 




Fig. 72. 



-The Falkenau-Sinclair Cement Test- 
ing Machine. 



*From manufacturers' circular. 



TENSILE STRENGTH. 



143 



load on the briquette is read directly. The advantages of this 
machine are the direct reading of the stress and the elimination 
of the errors due to the impact and weight of the falling column 
of shot; its disadvantages are the necessity of applying an initial 
load, the use of a spring balance which is less accurate and 
likely to introduce an undetected systematic error, and a rather 
compHcated arrangement for closing off the flow 01 shot, liable 
easily to get out of order. 

The Riehle machine (Fig. 73) eliminates the error due to 
initial loading by the 
use of a worm gear 
similar to that in the 
Improved Fairbanks, 
and, for stopping the 
flow of shot employs 
a piston valve, which 
is less easy to disar- 
range. Otherwise, it 
is very similar to the 
Falkenau-Sinclair. 

The capacity of the 
first two of these 
shot machines is 1,000 
lbs. , while the Riehle is 
made of both 1,000 
and2,ooolbs. capacity. 

An example of the 
spring balance type 
of cement testing ma- 
chine as made by Riehle is shown in iMg. 74. The stress is ap- 
plied by turning the crank by hand and its amount indicated on 
the dial. The dial gauge has about an inch and a half of moxc- 
ment, and as it descends allows the wedge at ihc rear i^VnW to 
drop and block the gauge and pointer from the shcxMc of a 
sudden recoil at fracture, as well as leaving the register of the 
maximum load. The gauge is then relieved by means ol the 
handle Ijar, the wedge withdrawn, and the pointer allowed to re- 
turn to zero. 11ie capacity is either ()00 or i,JOO lbs. as desired. 
Olsen and others make machines practically sinnlar. 




Fig. 73. — Shot Machine as Made by Riehle. 



144 



PRACTICAL CEMENT TESTING. 




Several other forms of apparatus for test- 
ing- briquettes have been designed, but 
none are in sufficiently general use to be 
considered. Of the forms of machine de- 
sig-ned to test the tensile strength of cement 
using- test specimens other than the nor- 
mal briquette, the Johnson ring- machine 
( Fig-. 75 ) is one of the best known. 
The principle of operation is to burst 
an annular ring one inch hig-h and half an 
inch thick by interior hydrostatic pressure. 
Such devices, however, although useful 
for certain classes of experimental work, 
are entirely impracticable for ordinary 
routine. 

In either a permanent or a field laboratory, the shot ma- 
chines will be found to be the most serviceable type for every day 
work, since they are quick to operate, have few parts to get out 



Fig. 74, — Cement Tes- 
ter of the Spring 
Balance Type. 




Fig. 75. — The Johnson Cement Testing Machine. 



TENSILE STRENGTH. 



145 



of order, and give sufficiently accurate results. For experi- 
mental research, however, the long lever machines are prefer- 
able on account of their greater accuracy. The attachments 
for compressive and transverse tests are also a valuable feature 
of the latter type. The author uses a long lever machine for 
experimental, and a shot ma- 
chine for routine work, arid 
believes this arrangement is the 
best for permanent laboratories. 
For the engineer making only 
occasional tests, the spring 
balance type is cheap, occu- 
pies but little space, and gives 
a fair approximation of the 
true values. 

Form of Clip. — The standard 
form of clip ( Fig. 76 ) recom- 
mended* by the Committee of 
the American Society of Civil 
Engineers has rigid bearing sur- 
faces of brass, 1% ins. apart and 
% in. wide, this last distance be- 
ing shaped to fit the contour of 
the briquette. A bolt in the 
middle of the clip prevents the 
.bearings from spreading. This 
rigid bearing is defective in 
that if there is any appreciable 
change in the volume of the 
briquette the contour of its 
sides and that of the bearings no 
longer agree and the bearing 
reduces to a line instead of an 
area, thus creating a greater tendency to breaking in ilio clii>. 
To overcome this, many automatically adjustable hearing iK- 
vices have been proposed, including roller bearings, conical 
bearings, adjustable plate bearings, pin-connected clips and 
several others. These devices when in iio(M\ working K^v^c\■ 
generally reduce slightly the i)roi)(irti(in of clip breaks, but i^ivc 

♦See Appendix A. 




Fig. 76.— The Standard Fi)rni of 
Clip Recommended by the A. S. 
C, E. Committee. 



146 PRACTICAL CEMENT TESTING. 

strength values no greater than with the rigid form. The great 
objection to these adjustable bearings is the difficulty in keep- 
ing them clean and working smoothh', and if a small piece of 
cement becomes wedged in them, thus preventing freedom of 
motion, they are much worse than the rigid bearing. Roller 
bearings are especially objectionable in this particular, being 
easily clogged and then wearing flat. 

The use of cushioned clips has been frequently attempted 
by inserting strips of rubber, blotting paper or tin-foil, between 
the briquette and the bearing, but, although efTfective in pre- 
venting clip breaks, they give much lower strength values. 
Sabin^ states that in a series of tests cushioned clips gave but 
86 per cent, of the strength of briquettes tested in bare clips. Tests 
by the author gave a smaller difference, but still an appreciable 
lowering of the strength. In routine work these cushions are 
annoying and unsatisfactory. 

The reason that briquettes break in the clips must be that 
cross-strains are developed, which cause premature failure, and 
furthermore, it is evident that the strength at the least section 
of the briquette should be greater than the result obtained 
from a clip break, because a stress of that amount has not pro- 
duced failure. Nevertheless, it is a fact that breaks in the clips 
average a greater strength than those breaking in the least 
section. Comparison of these values by the author on over 
1,000 briquettes showed the clip breaks to average about 4^ 
greater than those breaking normally. Sabin found this dif- 
ference to average 3^%, and says "this result is easily accounted 
for by saying that some of the briquettes that broke in the 
small section were made to do so by the cross-strain introduced 
by imperfect adjustment in the clips." This reason, however, 
seems scarcely sufficient. 

The standard form of clip will give* about 5 to 10 per cent, 
of cHp breaks for neat cement briquettes, and almost none for 
sand briquettes. It is far the quickest and most convenient 
to operate, never gets out of order and will be found the most 
satisfactory for ordinary routine. The use of strips across the 
backs of the clips for purposes of adjustment has been found 
inconvenient, better and quicker adjustment being made on clips 
open on both faces. 

*"Cement and Concrete," by L. C. Sabin. 



TENSILE STREXGTH. 



H7 



Great care should be exercised to see that the briquettes are 
properly centered and the bearings immediately over each other. 
Johnson* states that an eccentricity of i.' i6-in. may reduce the 
tensile strength by as much as 15 or 20 per cent. 

Rate of Stress. — The more rapidly the load is applied to a 
cement briquette, as with all other materials, the greater will 
be the results obtained. The diagram (Fig. 77) gives the re- 
sults of tests made by Henry Faija in 1883, while Fig. 78 rep- 
resents a short series made by the author. The trend of both 
diagrams is seen to be similar. Both of these diagrams were 

based on tests of 
neat Portland cement 
briquettes only, but 
Table XXXVIII 
shows that the same 
law applies to bri- 
quettes of all composi- 
tions. The standard 
rate for many years 
has been 400 lbs. 
per minute, but the 
recent Committee 
of the American 
Society of Ci\'il 
Engineers has in- 
creased this rate of 



^J^ 



/s% 



/0% 



SP/, 























































^ 




















































^ 


\ 
























s 


\ 
























^^ — 




\ 






















r 






\ 


■\ 


















1 












-^ 


















T//W, 


^ p^ 


9 //^/ 


'""//?. 


If/ / 


\^ / 


.Sq 


[^ 


^_. 






OSIG. 


r: 





^ 





6 





6 





/O 







JT^. 



Fig. 77. — Diagram Illustrating the Effect 
of Rate of Application of the Load on 
the Tensile Strength of Cement. ( From 
Faija's Tests.) 

applying the load to 600 lbs., which commends itself both for 
increased rapidity in testing, and also that, as shown by the dia- 
grams, small variations from the standard have less effect at 
the higher rate. Any testing machine should be carefully set 
and made to operate regularly at this fixed speed. In a long 
lever machine it must be remembered that it is the poise that 
must move uniformly, not the wheel applying the load. 

Wet Briquettes. — Cement bric|uettes nuist always be broken 
as soon as the\ are removed from the tanks and before iliey 
have commenced to dry out. I[x]uu-inients have shown thai 
this first drying out greatly lowers the strength, especially of 
neat briciuettes, and that half an hour's time mav apj^reciablv 
affect the results. 



♦"Materials of Construction.' by .1. 



)linson. 



148 



PRACTICAL CEMENT TESTING. 



Xo more than 5 neat, nor 10 sand briquettes, should be taken 
at once from the tanks, and placed in air near the testing ma- 
chine. If the storage tanks are at some distance from the ma- 



Rate 



per Minu+G. 

600 700 



800 




— • - - Average of 7 day tests. 

Average of 28 day tests. 

Curve of Average Strength 

Curve Showing Percent- 
age of Increase In Strength, 
Assuming Lowest Value as 
Unity. 
Points on 7 day Curve Based on 
Average of 40 Briquettes Each. 

Points on 28 day Curve Based 
on Average of 80 Briquettes Each, 
420 Briquettes in All. 



1.100 p 
9> 



1.080- 



1.060^ 



0) 
1.040 g^ 



1.020 



1.000 



Fig. 78.— Diagram Illustrating the Effect of Rate of Application of Stress on the 
Tensile Strength of Cement. ( From Tests by the Author.) 

chine, the briquettes ready for test should be kept in a pan 
filled with water placed conveniently near from which thev can 
be taken 3 or 4 at a time. 

Number of Briquettes. — The number of briquettes to be broken 



TABLE XXXVIII 



Effect of Rate of Applying the Stress, on 
Tensile Strength. 
(From Sabin's "Cement and Concrete.") 

/—Tensile Strength, Pounds per Square-> 



Cement 


Proportions 


Age 


1] 


ich, tor b« tress, Applied at 
Pounds per Minute. 


— 








100 


300 


500 


700 


900 


Portland 


Neat Cement 


7 and 14 days 


453 


485 


521 


520 


528 




" ." 


3 months 




590 


617 


622 


640 




I : 2 


3 " 


445 


467 


487 


507 


510 


Natural 


Neat Cement 


7 days 


150 


169 


186 




202 


<• 


i( a 


3 months 


309 


351 


363 


378 


390 




I : 2 


3 " 


255 


299 


327 


329 


354 



TENSILE STRENGTH. 149 

at each period depends upon the importance of the test, the ac- 
curacy desired, and the skill of the operators. In ordinary rou- 
tine, the author makes but 8 neat and 6 sand briquettes from 
each sample, breaking 2 neat briquettes at i, 7 and 28 days, 
and two sand briquettes at 7 and 28 days. If the average of 
these two values meets the requirements of the specification, 
or falls far below them, no other tests are made, but if the 
average is but slightly below, especially if one test is over and 
one under, one, or if necessary, both of the remaining two 
briquettes are tested to corroborate one of the two values. If 
the additional briquettes are not thus needed they are stored 
and broken at later periods for the accumulation of data. The 
testing of so few briquettes is, however, only possible where 
the operators have attained a high degree of skill and accuracy, 
and is not advised for the ordinary laboratory. Generally, re- 
ception tests should be made on 4 or 5 briquettes for each 
period, which may be reduced to 3 or 4, as the accuracy of the 
operators increases. For experimental work, or where espe- 
cial accuracy is desired, as in a possible case of litigation, at 
least 10 briquettes should be tested for each period. If the 
number of briquettes to be made from any one sanij^le is too 
great to be made from one mixing and moulding, the briquettes 
for each period should be taken equally from each moulding, 
that is, if 2 mouldings of 8 briquettes each are made, and 4 
briquettes are to be broken at 7 days, 2 should be taken from 
the first moulding, and 2 from the second. If gang moulds 
are used, and only one mixing is made, then briquettes for 
any one period should be taken from different gangs. and not 
from the same one. 

Average Values. — The result of the test is the arithmetical 
mean or average of the strength of the individual l)ri(|uettos. 
Some writers claim that the highest value and not the aver- 
age should be taken as the result, but this is manifestly inac- 
curate for the reason that the determination is not made to 
ascertain the greatest strength that the cement cau develop, but 
the strength it will attain when treated in accordance with cer- 
tain fixed conditions, wliich is only represented bv the aver- 
age. It is, of course, true that most of the irregularities intro- 
duced by careless mani])ulaticMi tend to lower, rather than in- 
crease, the strength, but it, nevertheless, may well happen tliat 



I50 PKACTICAL CEMENT TESTING. 

the highest vakie may also be the result of some abnormal con- 
dition and not be indicative of the true strength. 

Accuracy. — The accuracy of a test depends upon the skill of 
the operators in making uniform briquettes and upon the num- 
ber of individual values from which the average is computed. 
The accuracy of a series of tests is determined by computation 
of the probable error"^ of a single determination and of the 
mean. A skilled operator should always work with a probable 
error of not over 4 per cent, for a single briquette. Any test- 
ing in which the probable error of a single result exceeds 7 
or 8 per cent, is very inaccurate and is indicative of either gross 
carelessness, or of the use of a poor method. An approximate 
method of stating the accuracy of a series of tests is by means 
of the average departure from the mean which is the arithmet- 
ical mean of the individual errors. In cases where a long series 
of tests has been made to obtain a single result a method 
sometimes employed is to discard all values whose departure 
from the mean exceeds say 10 per cent., and then to average 
the remaining values for the final result. 

Thus supposing the 20 tests given in Table XXXIX. were 
made to determine the strength of sand briquettes at 28 days, 
all of them, apparently, being equally well made and broken. 
The mean value is 281 pounds; the probable error of one re- 
sult is 13.2 pounds, or 4.7%, of the mean, while that of the mean 
is 3.0 pounds, or 1.1%; the average error is 15.6 pounds, or 
5.5%. The probable error of the mean result is expressed by 
stating its amount with a plus or minus sign after the average. 
Thus to state that a cement has a strength of 281 pounds gives 
no indication of the accuracy of determination, but if it is stated 
that 20 tesiG gave a result of 281.0 + 3.0 pounds, the amount 
of dependence that can be placed on any value is positively 



* The probable error Is an error ol such a value that the probability of its being 
exceeded Is equal to the probability of Its not being exceeded. From the principles of 
the method of least squares, the probable error of a single determination, in a series of 
determinations of equal weight, is computed to be 

0.6745 






In which A •= the difference between anv one determination and the mean value of the 
series, and n = the number of determinations. The probable error of the arithmetical 
mean of the series is 

i A- ^n 



V^ A- ^, 
= — 
n (n — 1) y-D. 



TENSILE STRENGTH. 



151 



known. The method of correction by dropping vakies whose 
error exceeds ten per cent, of the mean is also shown in Table 
XXXIX., by which it is seen that the average is changed from 
281.0 + 3.0 to 282.9 + 2.3 pounds. This series of tests is of 
but indifferent accuracy. 



TABLE XXXIX.— Illustration of the Method of Computing Probable and 

Average Error, and of Correcting a Series of Determinations. 

/■ Original • ' Corrected ^ 

Square Square 

No. Value Error of Value Error of 

Error Error 

1. 271 10 100 271 12 144 

2. 277 4 16 277 6 36 

3. 266 15 225 266 17 289 

4. 286 5 25 286 3 9 

5. 284 3 9 284 I I 

6. 252 29 841 

7. 307 26 676 307 24 576 

8. 271 10 100 271 12 144 

9. 298 17 289 298 15 225 

10. 251 30 900 

11. 279 2 4 279 4 16 

12. 272 9 81 272 II 121 

13. 248 33 1,089 

14. 316 35 1,225 

.15. 267 14 196 267 16 256 

16. 285 4 16 285 2 4 

17. 282 I I 282 1 I 

18. 303 22 484 303 20 400 

19. 295 14 196 295 12 144 

20. 310 29 841 

Total 5,620 312 7,314 4»243 ^S^ 2,366 

Original: — Lbs. "0 of Mean 

Mean 281.0 

Probable error of one result i3-2 4-7 

" " '' mean 3-0 '•' 

Average error i5-6 5-5 

Total range 68.0 24.2 

Corrected: — 

Mean 282.9 

Probable error of one result ^-^ 3* ' 

<• " "mean 2.3 0.8 

Average error io-4 3-7 

Total range 4i-0 '4-5 

Of course, this method of stating accuracy and correcting 

results applies more to experimental work or other cases where 
extreme accuracy is desired. In ordinary routine the range 
in the values of 3 or 4 briquettes should not exceed \o'/c, whdr 

the probable error of a single value should not average over 
3^ or 4 per cent. 



PRACTICAL CEMENT TESTING. 



The Tensile Strength of Cement. — On account of the many 
irregularities in the testing of briquettes, as well as the complex 
influences, both interior and exterior, operating upon the ce- 
ment, the curve of hardening of any one series of tests will 
present many apparent anomalies. The average values ob- 
tained in the Philadelphia Laboratories up to a period of one 
year are shown in Fig. 79, the curves of the neat and 1 13 sand 
briquettes being based upon an average of over 150,000 bri- 
quettes, while the other curves are based upon 300 to 500 
values each. The sag in the curve of the neat briquettes is plain- 
ly evident and the probable explanation of this condition has 
already been given.* After a period of one or two years the 




MOS 



10 MOS 



12 MOS 



Fig. 79. — The Average Strength of Portland Cemt nt, ( From Tests by the Author. ) 

values again begin to show retrogression from which there is 
no apparent recovery. This, apparently, is due to a change in 
the structure of the cement, for up to that time the fracture ap- 
pears dull and earthy, while later it becomes distinctly glassy 
and brittle, thus making more decided the effect of the irregu- 
lar crushing and cross-breaking strains that act in the least 
section of the briquette. It is probable, therefore, that the pure 
tensile strength is never developed after this change in struc- 
ture takes place, and hence the results show an apparent 
weakening although the real structural value of the material 
is in no wise affected by the alteration. This action also is de- 
veloped to a far greater extent in the small mass of a briquette 
than could take place in the large volumes of construction work, 

*See page 103. 



TENSILE STRENGTH. 153 

and although often existing in apparently alarming proportions, 
it need never cause anxiety as to the safety of the structure 
unless accompanied by a noticeable change in volume or by 
actual disintegration. 

There have been many formulas proposed by which the 
strength of cement at any period may be computed, if the values 
at 7 and 28 days are known, but they all assume that the rate 
of hardening progresses according to some definite law, and 
thus fall into such positive error that they fall little short of 
being absurd. 

It should be stated that both the first sag and final retrogres- 
sion in the curve of neat tensile strength is mucTi more marked 
in the case of cements manufactured by the rotary kiln process 
than in those made in stationary kilns, although there is but 
little, if any, difference in the structural value of the two classes 
of material. The difference in briquettes of sand mortar is less 
apparent. 

Interpretation of Results. — Specifications for the tensile 
strength of cement usually stipulate merely that the niaterial 
pass a minimum strength requirement at 7 and at 2'^ days, and 
the requirements, moreover, are so easily met that on!}- a de- 
cidedly inferior cement will fail to pass them. It must not be 
understood, however, that the specification requirements should 
be raised, since m.any old and well seasoned cements which 
make the best material for service might then be rejected. The 
proper grounds for the judgment of the tests of tensile strength 
are four in number: — that both neat and sand bricjuettes shall 
pass a minimum specification at 7 and at 28 days ; that the neat 
value at 7 days shall not be excessively great; thai there sliail 
be no retrogression in the neat strength between 7 and 28 days ; 
and that the strength of the sand bri(|uettes between these 
periods shall increase at least to or 15 i)er cent. It must, more- 
over, be remembered that the sand test is the true crileri(Mi of 
strength, and no cement failing in these tests should be aecepte.I 
even if tlie neat results are excellent. If the condilions are re- 
versed, however, the sand tests passing and ihe neat fail- 
ing, it may be justifiable to permit the use of the ninterial. pro 
vided there is no acroini):m\ ing indieiition ol unsoundness. 

The reason that the strength of cement shall satisfy a mini- 
mum rec|uircmcnt is obvious. The objection to a high neat 



154 



PRACTICAL CEMENT TESTING. 



test at seven days is that it usually indicates an over-limed ce- 
ment, which is practically certain to develop a decided retro- 
gression in 28 days, and is also more liable to unsoundness. 
An abnormal amount of sulphate of lime may also produce a 
similar effect. Portland cement tested neat in accordance with 
the method given and developing a strength in 7 days of over 
850 pounds should be looked upon with suspicion and gener- 
ally ought to be held for the 28-day test before allowing it to 
be used. Cement showing a retrogression in the strength of 
neat briquettes between 7 and 28 days is not necessarily of 
poor quality, but it may be considered as inferior to those giv- 
ing a good increase. On cements testing below 750 or 800 
pounds at 7 days, the lower the 7-day results, the more serious 
becomes any subsequent falling off in strength. If testing below 
700 pounds at 7 days, retrogression should mean rejection. In 
general, the greater the increase in strength between specifica- 
tion periods, the greater will be the strength ultimately attained. 
Thus one testing 550 and 700 pounds at 7 and 28 days is usually 
preferable to one testing 750 and 800. 

Cements failing to pass the sand requirements, or those not 
increasing in the sand strength, should not be accepted. Retro- 
gression in sand strength is indicative, in the majority of cases, 
of ultimate complete failure. 

A fair strength specification for Portland cement tested in 
accordance with the given method is 500 pounds for 7, and 
600 for 28 days, for neat briquettes, while those made of i part 
cement to 3 parts standard quartz should exceed 170 and 240 
pounds at the same periods. If Ottawa sand is used, the sand 
requirements should be increased to 200 and 280 pounds. On 
these figures material passing the 7-day tests and failing at 28 
days is unsafe, while one failing at 7 and passing at 28 may be 
accepted. Additional security may be obtained by specifying a 
maximum neat strength at 7 days (from 850 to 900 pounds), and 
an increase of 10 per cent, in the sand strength between 7 and 
28 days. 

One other point that must always be borne in mind is that 
cement has no absolute strength, but the strength is that de- 
veloped by a certain process of manipulation ; if, therefore, 
the process varies, the results will also. For this reason the 
method to be employed in obtaining the results should be a 



TENSILE STRENGTH. 155 

feature of every strength specification. In many cases, after 
the rejection of a shipment, those furnishing the material have 
tests made by private laboratories and apparently disprove the 
original tests, but such tests deserve no consideration whatever, 
unless it be proven that the methods employed were identical 
in both cases and that both conformed to that stipulated in 
the specifications. An experienced operator may obtain al- 
most any result from any cement by changes in the manipulation. 
The following rules for the acceptance or rejection of ma- 
terial on the results of the tensile test represent safe and con- 
servative practice : - 

At 7 days : Reject on a decidedly low sand strength. 

Hold for 28 days on low or excessively high neat 
strength, or a sand strength barely failing 
to pass requirements. 

At 28 days : Reject on failure in either neat or sand strength. 
Reject on retrogression in sand strength, even 

if passing the 28-day requirements. 
Reject on retrogression in neat strength if there 
is any other indication of poor quality, or if 
the 7-day test is low — otherwise accept. 
Accept if failing slightly in either neat or sand 
at 7 days and passing at 28 days. 



CHAPTER X. 

SOUXDXESS.* 

Definition. — The soundness of cement may be defined as that 
property which resists any force tending to cause disintegra- 
tion or lack of permanency in the structure, and since, if such 
disintegration occurs, it is usually accompanied by change of 
volume, a sound cement is frequently termed "volume con- 
stant." This determination of "constancy of volume" or "sound- 
ness" is unquestionably the most important phase of the test- 
ing of cement, for although a sample may pass all the other 
tests with ease, if it is unsound, and will eventually disintegrate 
on the work, it is evidently worse than worthless for constructive 
purposes. 

Causes of Unsoundness. — The most important factor operating 
in a cement to cause unsoundness is an excess of lime, either 
free or loosely combined, which has not had opportunity to have 
become sufficiently hydrated. The presence of this lime may 
be due to incorrect proportioning, to insufficient grinding of 
the raw materials, to underburning, to lack of seasoning, or 
to coarseness of the finished cement which prevents perfect 
hydration. Excess of magnesia or the alkalies and the pres- 
ence of sulphides are also sometimes responsible for disintegra- 
tion, while the presence of sulphate of lime may act in either 
direction, occasionally causing unsoundness, but generally tend- 
ing to make good an otherwise unsound cement, at least so 
far as laboratory tests are concerned. 

Although an excess of uncombined or loosely combined lime 
is generally conceded to be the most potent factor in causing 
unsoundness, it is nevertheless impossible to tell by any 
known method of chemical analysis just what proportion of the 
total lime present exists in this dangerous condition, so that 
unless any injurious constituent is present in gross excess, an- 

*Much of this chaDter is quoted from a paper on "Soundnegs Te^s of Portland 
Cement," read by the author before the American Society for Testing Materials. 
July. 3, 1903. 



SOUNDNESS. J -7 

alysis gives no indication as to the soundness of the material.* 
Excluding, therefore, the effect of composition, which is usual- 
ly indeterminable, the conditions most affecting the soundness 
of cement are its age or seasoning, and its fineness. 

Effect of Age. — The property of a cement most affecting the 
results of the tests for soundness is its age or the amount of 
seasoning it has undergone. Almost every cement, no matter 
how well proportioned and burned, will contain at least a small 
amount of free or loosely combined lime, which will often cause 
unsoundness if used or tested at once. This lime, however, 
will hydrate in a very short time on exposure to the air, thus 
rendering it inert and preventing any expansive action. It will, 



TABLE XL.— Effect of Age of Cement on Results of Boiling Test. 
(Tests by the Author.) 



Age of 
Cement 
When 
Tested 


1 

day 


Tensile St 


rength 

^1 : a Sand-^ 

7 28 

days days 


Normal Pat Tests 
28 Days 28 Days 
in Air in Water 


Boiling 
Test 


7 28 
days days 


I week 


550 


765 762 


171 


225 


Curled Slightly 
and soft. checked. 


Partly dis- 
integrated. 


2 weeks 


548 


767 771 


170 


246 


Slightly Slightly 
curled. curled. 


Checked and 
cracked. 


3 " 


492 


718 763 


182 


244 


"O.K." "O.K." 


Shghtly 
checked. 


5 " 


427 


692 747 


183 


249 


"O. K." "O. K." 


Sound. 



therefore, be found that, in a large majority of cases, if a ce- 
ment failing in the normal or accelerated tests be stored for 
two or three weeks, this unsoundness will (Hsaj-Jpear, and the 
cement pass the tests with ease. A typical case of this is shown 
in Table XL., the specimens on which the boiling test was 
made being also shown in Mg. 80. It will be noticed that in 
this instance the cement has been made thoroughly sound by 
a seasoning of five weeks. The early strength values of the 
neat tests are also seen to fall off decidedl), while the saiul tests 
generally show a slight increase. 

Effect of Fineness. — Coarseness of grinding is also a frO(|ueiit 
cause of unsoundness for the reason that the larger particles 
are not readily susceptible to liydratii^n. and contain for a h^ng 
period of time expansive elements, whicli very raj^idlv develop 

♦For further disousslon on this point see Chnptt<r Xi. 



158 



PRACTICAL CEMENT TESTING. 



a disintegrating action when treated in the accelerated tests, 
and even in the normal tests often induce failure. A study of 
the tests given in Table XLL, the boiling test specimens of 
which are shown in Fig. 8i, will clearly show that failure in this 
instance was caused by the presence of expansives in the coarser 
particles. 

Methods of Determining Soundness. — The soundness of cement 
is customarily determined in one or more of the three following 





One Week Old. 



Three Weeks Old. 





Two Weeks Old. Five Weeks Old. 

Fig. 8o. — Illustrating the Effect of Age on Soundness. ( See Table XL.) 

ways : — by direct measurement of the change in volume ; by 
observation of specimens kept in a normal environment — 
called "normal" tests ; by observation of specimens so treated 
by the action of heat or chemical salts that any disintegrating 
action is hastened — called ''accelerated" tests. 

Measurements of Expansion. — Soundness was often tested by 
this method some years ago, but at present it has been vir- 



^1 



SOUNDNESS. 



159 





No. 1.— Cement as Received 
(very coarse) . 



No. 4.— Cement Finely Ground (tested one 
week later than Xo. 1) . 





No. 2.— Cement as Received (sifted to pass 
No. 200 sieve). 



No. 5.— Cement Finely Ground (tested two 
weeks later than No. 1). 




No. 3.- Cement Finely Ground (tested same 
time as No. 1). 




No. (>— C'eiufiiL as Kect<ived (tt^tod 
two weeks hiter than No. 1). 



Fig. 81. — Illustrating the F.ti'ectcf Fineness on the Hoilint,' Test. (SeeTable M.l.) 

tually abandoned in llic I'nitcd Stales. alili(nii;li .still cnijilovod 
considerably abroad, it has boon definitely shown that oven 
an api)arcntly hii^h expansion or contraction is not necessarily 
indicative of disinteo-raiion, wliik on the other hand cases have 
frcc|ncntly been observed in which a cement has remained sonnd 
and withont appreciable change in vohnne lor several months. 



i6o 



PRACTICAL CEMENT TESTING. 



then suddenly begun to disintegrate and finally failed entirely. 
In construction work, an expanding cement is deemed bene- 
ficial by many prominent engineers, as compensating in a meas- 
ure for settlement. Small specimens 
of cement kept in the laboratory 
will usually show contraction w^hen 
kept in air, and expansion when 
kept in water. 

For measuring the amount of 

change in volume, the Bauschinger 

apparatus, shown in Fig. 82, is one 

of those most generally used. The 

principles of this apparatus can be 

plainly seen from the figure. The 

bars of cement are about 5 square 

centimeters in section and 10 cen- 

FiG. 82.-Calipers for Measuring timeters in length, and have small 

Expansion, According to Ban- ^^^^^^ embedded in the ends tO 

schinger. , ... 

serve as bearmg pomts for the 

micrometer screw, which will indicate a change in length of 
.0005 centimeters. The vertical needle and spring on the left 




TABLE XLI.— Effect of Fineness of Cement on Results of Boiling Test. 
(Tests by the Author.) 

Condition of Cement No. 50 No! HW No. 200^ Boiling Test 

As received 0.5 13.2 33.4 Badly checked and cracked. 

Same cement sifted 0.0 0.0 0.0 Sound. 

Same cement ground 0.0 0.6 3.0 Checked and cracked. 

Ground cement, i week later 0.0 0.6 3.0 Very slightly checked. 

•' " 2 " *' 0.0 0.6 3.0 Sound. 

As received 2 " " 0.5 13.2 33.4 Checked and cracked. 

of the figure insure a uniform pressure of the screw against the 
bearing plate. 

The Le Chatelicr apparatus (Fig. 83) is also infrequently em- 
ployed for this purpose and is said to be more easily oper- 
ated than any of the other forms. It is described by Le Chate- 
lier as follows: *'A much more simple and yet sufficiently pre- 
cise measurement of the expansio.n can be made by letting the 
cement harden in cylindrical moulds of a diameter equal to 
their height, constructed of metal, slit along the generatrix and 
provided on each side of the slit with two long needles, which 



SOUNDNESS. 



i6i 



serve to magnify any widening of the slit. The widening is 
equal to the enlargement, not of the diameter, but of the cir- 
cumference of the cylinder of cement." 

This apparatus may be employed not only on specimens kept 
at normal tempera- 

R ul X' 



3 



<-5/— >l 




Fig. 83. —The LeChatelier Tonj 



tures, but also on 
specimens which 
have undergone 
some form of accel- 
erated test. The 
method of making 
this test, recommen- 
ded by the Engi- 
neering Standards 
Committee in the British Standard Specifications,"^ is as follows : 
*'The apparatus for conducting the Le Chatelier test consists of 
a small split cylinder of spring brass or other suitable metal of 
0.5 millimeters in thickness, 30 millimeters internal diameter, 
and 30 millimeters high, forming the mould, to which on either 
side of the split are attached two indicators 165 millimeters 
long from the center of the cylinder, with pointed ends." 

'Tn conducting the test, the mould is to be placed upon a 
small piece of glass and filled with cement gauged in the usual 
way, care being taken to keep the edges of the moulds gently 
together while this operation is being performed. The mould 
is then covered with another glass plate, a small weight is 
placed on this and the mould is inmiediately placed iii water at 
58 to 64 degrees Fahr., and left there for 24 hours." 

'The distance separating the indicator points is then meas- 
ured, and the mould placed in cold water, which is brought to 
a boiling point in 15 to 30 minutes, and kept boiling for six 
hours. After cooling, the distance between the points is again 
measured, the difYerencc between the two measurements repre- 
senting the expansion of the cement." 

While there exist many other forms of apparatus for making 
this determination, they all are more or less similar in princi- 
ple to those given, ami since lliis test is selchmi. il ever, re- 
quired in this country, it will not be considered furtiuT. I'ossi- 
bh allusion should l)e made to the once poi)nl:ir "lainp-chim- 



•See Annendlx B. 



l62 PRACTICAL CEMENT TESTING. 

ney" test, which was based upon the same idea, and consisted 
of filling a lamp chimney with a thin paste of cement, cracking 
of the chimney in hardening showing expansion, and being 
considered a failure. This test, however, was so crude, and the 
inferences drawn from it apt to be so erroneous that it has 
been almost entirely abandoned. 

Normal Tests. — Normal tests consist of making, from pastes 
of neat cement, pats having thin edges, being thus more sus- 
ceptible to any disintegration, keeping them in air and in water 
under normal conditions and observing them from time to time, 
to see whether they remain hard, sound and straight. This, 
undoubtedly, is a perfectly fair test, with a possible exception, 
in that a neat cement is always more liable to disintegrate than 
a sand mortar, and hence a cement miay occasionally fail in the 
normal tests, while the mortar in which the cement is used may 
be perfectly sound. Generally, however, failure in the normal 
tests is indicative of unfitness for use. 

The common form of specimen for these tests is a circular 
pat, 3 or 4 inches in diameter, about f to J-inch thick at the 
center, and tapering to a thin edge on the circumference. Some- 
times the specimens are made in the form of a wedge, w^ith a 
thin edge on only one side. These pats should be made of 
neat cement of normal consistency and should be kept in either 
air or water at a temperature of as near 70 degrees Fahr. as 
practicable, although small variations from either normal con- 
sistency or normal temperatures fortunately seem to exert but 
little influence on the results. A most important point, how- 
ever, always to be observed, is that the pats, as soon as made, 
be placed in a damp closet or covered with a damp cloth until 
they have entirely hardened (best for 24 hours), since other- 
wise, if allowed to dry out too quickly, they may show shrink- 
age cracks which by a novice might be mistaken for failure. 
It is also common practice to rnould the pat on a small square 
of polished glass, and to allow it to remain attached to this 
glass during the entire period of the test. 

The specification test is generally for 28 days, although pats 
should be kept for a much longer time if reliable data concern- 
ing them are desired, and it is good practice to examine these 
pats at intervals of 3, 7, 14 and 28 days from the date of mak- 
ing, and then at such intervals as may be desired. To thorough- 



SOUNDNESS. 



163 



ly examine a pat, it should be ascertained (i) whether it has 
left the glass, (2) if it has left the glass, whether it is straight 
or curved, (3) whether it has developed cracks due to shrinkage, 

expansion, or disintegration, 
(4) whether it is blotched, (5) 
whether the glass is cracked. For 
examination of the curvature a 
small steel straight-edge is con- 
venient. 

Pats kept in water should 
be straight, free from cracks, 
and not blotched. Pats in air 
should not show disintegration 
cracks, should not be excessively 
curled, nor blotched. Cracking the 
glass in the water pat, expansion cracks and slight curvature 
in the air pat, and leaving the glass in either air or water are 
not considered to be indicative of injurious properties. About 
30% of the water and 70% of the air pats leave the glass in 
seven days' time. 

Since a person with limited experience in cement testing 
often desires to make and test normal pats, the following dia- 
grams are given to illustrate the common forms gf failure in 
these tests : 

Figure 84 represents a normal pat in good condition. 




Fig. 84. —Normal Pat. 





Fic. 85. — ShrinkaRC Cracks. 

Figure 85 rcprcsenls shrinkage cracks. Those arc iluo or 
dinarily to the use of too wet a mixture, or to loo tiuick dry- 
ing out. If the pats arc left exposed to dry air during setting. 



i64 



PRACTICAL CEMENT TESTING. 



these cracks frequently develop. Shrinkage cracks ordinarily, 
therefore, indicate only a lack of care in manipulation, and not 
dangerous qualities of the material. 





Fig. 86' — Expansion Cracks. 

Figure ^6 illustrates cracks caused by expansion or con- 
traction. In the air pats these cracks are developed in nine- 
tenths of those adhering to the glass, and unless very decidedly 
marked, are not dangerous. If existing in the water pats, how- 
ever, it usually indicates an inadmissible proportion of expan- 
sive elements. 

Figure 87 represents pats curling away from the glass, but 
still adhering to it. This is due to the same action that causes 
the expansion cracks shown in Figure ^6, and can be consid- 
ered identical in cause and effect. 




Fig. 87. 



-Pats Curling Away from the 
Glass. 



B C 

Fig. 88. —Pats Which Have Left the 
Glass, Showing Change in Volume. 

Figure 88 shows pats which have left the glass (A) by lack 
of adhesion, (B) by contraction, and (C) by expansion. (A) 
is never dangerous in either air or water. (C) is only danger- 



SOUNDNESS. 



165 



ous when existing in a marked form. (B) rarely, if ever, occurs 
in water, but in air often is indicatve of dangerous properties. 
Air pats developing this concave curvature generally disinte- 




FiG. 89.— Pats Which Have Cracked the Glass, 
grate eventually. A curvature of about a quarter of an inch 
can be considered about the limit of safety in a 3-inch pat. 

Figure 89 indicates a peculiar condition in which the pat is 
perfectly sound and hard, but the glass on which it is made is 
badly cracked. This has been often erroneously attributed 
to chemical action, but is probably due entirely to the expan- 
sion of the pat, the adhesive strength of the cement to the glass 
exceeding the strength of the glass itself. It is only found in 
the water pats, and is rarely indicative of dangerous qualities. 

Figure 90 represents blotching which usually is indicative 
of either underburning or adulteration. This condition should 
always be followed by an investigation of the causes produc- 
ing it, which may or may not warrant rejection of the shipment. 

Figure 91 shows the radial cracks 
of incipient disintegration. These 
are the danger marks to be looked 
for in the normal pats, and their 
presence is always sufficient to war- 
rant condemnation. 

Figure 92 shows examples of 
comi)lete disintegration, which al- 
most invariably begins first by 
showini^'' the radial cracks of 
Fig. 90.~A Blotched Pat. Figure (j I . 




1 66 



PRACTICAL CEMENT TESTING. 



The great objection to the normal pats as an acceptance test, 
is the length of time often required for unsoundness to de- 
velop, cases being on record where disintegration only com- 




FiG. 91. — Radial Cracks. 

menced after five or six years. In the author's laboratory, but 
45 per cent, of the failures in the normal pats occur within 
28 days. It is frequently necessary in practice to use a ship- 
ment of cement within a week after reception so that only a 
seven-day test is possible, and in such a case it is evident that 
the normal tests are almost worthless. It is to overcome this 
difficulty that the accelerated tests have been devised. 

Accelerated Tests. — These accelerated tests are designed to 
hasten the action of the expansive ingredients and to produce 
the same results within a few hours or at most a week, for which 




Fig. 92. — Disintegrated Pats (See also Figs. 99 and 100). 

the normal pats require weeks, months or even years. Of the 
many varieties of accelerated tests the following are the best 
known and most used. 



SOUNDNESS. 



67 




The Warm Water Test.— This was one of the first accelerated 
tests devised, and was proposed by Henry Faija in 1882. It 
consists in placing a pat, made of neat cement of normal con- 
sistency, and moulded on g^lass, in a 
closed vessel over water maintained 
at a temperature of 115 deg-rees Fahr., 
until it becomes hard set, after which 
it is lowered into the water for the re- 
mainder of 24 hours. The orig^inal 
apparatus desig-ned by Faija is shown 
in Fig, 93, its construction being 
obvious. 

A modification of this test was 
originally recommended by the Com- 
mittee of the American Society of Civil 
Engineers*, and consisted in keeping 
a pat for 24 hours in moist air, and then 
_^f^ immersing it in cold water 
Tmt^ which was slowly raised to 
Fig. 93.— Faija s Hof Water Apparatus. 115 deg:rees Fahr., and main- 
tained there for 24 hours. 
The Hot Water Test. — Since the temperature of 115 degrees 
Fahr. was often considered too low, Deval and others have 
advocated the same test, except for maintaining the water at 
a higher temperature, different experimenters recommending 
temperatures of all the way from 130 to 200 degrees Fahr. 

Maclay's Tests. — These were the first accelerated tests used 
in the United States as a specification recjuirement, and con- 
sisted of making on glass plates six pats from neat cemeni of 
normal consistency. One of these as soon as made was placed 
in a steam vapor bath having a temperature of from H)^ to 200 
degrees Fahr.; the second put in the same bath as soon as it 
could bear the one-pound Gillmorc needle ; the third in double 
this time ; the fourth after 24 hours. The fifth was jilaced in 
fresh water at 60 degrees l^\ahr. as soon as set, ami the sixth kepi 
in moist air at the same temperature. 'I'lu- first four of these 
pats remained in the vapor for three hours, then were inuuersecl 
in hot water (about 200 degrees Fahr.) tor ji lionrs eacli. wlien 
they were taken or.l and examined. Mr. Macia\ sa\s "the 



"This lest was iibandoiKMl In llu- ainciuliiu-nis atl(n>l»''l In UH>I. 



l68 PRACTICAL CEMEXT TESTIXG. 

cracking or swelling oi :he nrst pat alone can generally be dis- 
regarded." 

The Boiling Test. — This method was first proposed bv 
Michaelis in iS~o, and consists of making from neat cement 
paste, small balls about 5 centimeters in diameter. These balls 
are kept in moist air for 24 hours, then placed in cold water. 
which is gradually (in about half an hour") raised to boiling and 
maintained for six hours, when the specimens are removed and 
examined. \'arious experimenters have proposed many modi- 
fications of this test, some using pats instead of balls, others 
allowing the specimen more or less time, to harden before test- 
ing, and still others making the duration of the test longer or 
shorter. 

The Steam Test. — This test is recommended by the Committee 
of the American Society of Ci\-il Engineers,"*" and consists of 
making a pat of neat cement paste of normal consistency, keep- 
ing it in moist air for 24 hours, then "exposing it in any con- 
venient way in an atmosphere of steam, above boUing water in 
a loosely closed vessel, for 3 hours." 

The Steam and Boiling Test. — A combination of the two fore- 
going methods is employed in several laboratories, consisting 
of putting a 24 hour old specimen in steam for 3 hours, then in 
boiling water for from 2 to 6 hours. 

Other forms of accelerated tests less extensively used are the 
following : 

The Kiln Test. — A cake of neat cement is made on a sheet of 
moist blotting paper upon a glass plate, and after it has set the 
cake is detached from the paper and preserved in moist air for 
24 hours. It is then heated to 212 degrees Fahr. upon a metal 
plate in an air bath, heated with boiling water, imtil no more 
moisture is evolved, this requiring about 3 hours. This test has 
been modified by using a rrtoist atmosphere in place of dr\' air. 

The Heintz Ball Test. — A ball of neat cement paste about 2 
inches in diameter is made and, when hard set. is placed on a 
thin iron plate above a Bunsen burner. The heat at first is 
gradually applied, then increased untU the plate is red hot. The 
test is completed when no further moisture is evolved from the 
ball, this point being obser\-ed by condensation on a glass plate. 

•See Appendix A. 



SOUNDNESS. 169 

Prussing's Press Cake Test. — This consists of making a dry mix- 
ture of neat cement, using from 5 to 8 per cent, of water, plac- 
ing it in a mould and pressing it with a die under a load of 50 
atmospheres. Two of these cakes are made, allowed to harden 
24 hours in moist air, then one of them is used for the normal 
water test, and the other is placed in cold water for 2 hours, and 
then put into a water bath having a temperature of from 90 
to 100 degrees C, where it is examined at the expiration of 4, 
and of 24 hours. 

The Steam Pressure Test. — Erdmenger devised this method, 
which consists of allowing pats to harden 3 days in water at 
ordinary temperatures, then exposing them for 6 hours to steam 
at a pressure of from 3 to 20 atmospheres. 

Deval's Hot Test. — This test consists of comparing the tensile 
strength of briquettes of sand mortar, one to three, at the age 
of 7 and 28 days when preserved in water at 15 degrees C, and 
at the age of 3 and 7 days when in hot water at 30 degrees C. 
It has also been proposed to test neat briquettes in a similar 
manner. 

Le Chatelier's Test. — This method is to determine the expan- 
sion of a cylinder of cement which has l)ecn subjected to lioil- 
ing.* 

Chloride of Calcium Test. — Pats of cement are made of cement 
mixed with water containing 40 grammes of ciiloride oi calcium 
to the liter, and, after setting, are immersed in the same solution 
for 24 hours. 

In addition to the foregoing, many other methods for c(^ndiict- 
ing accelerated tests have been devised, ])ul their emplovnu-nt 
is too infreciuent to warrant consideration. 

Methods of Conducting Accelerated Tests. — \\ ith the possible 
exception of the Deval hot briciuette test, only those forms of 
accelerated test made in steam or in hot or boiling water are 
employed in the United States in routine testing, anil there- 
fore the others will not be discussed further than to state tliat 
the results obtained from them give no better indication of ixo0i\ 
quality, and that in general they are more difTicult to make and 
less easy to interpret properly. 

The ol)jection most fre(|U(Mitly made to ;u'i-rKra!rd u.s'.s .mu 

♦DoBcrlbed on page 1(U. 



Ijo PRACTICAL CEMEXT TESTIXG. 

particularly to the boiling test, is the great variance in the 
methods used, different laboratories usin^- different forms of 
test piece, and different periods of time before the test and for its 
duration. The variance in the results obtained under these 
several methods is, however, far less than it is generally sup- 
posed. The form of the test piece has practically little or no 
influence on the results, whether it be a cake, a ball, a wedge, 
or a pat. if the duration of the test be sufficient. The only advan- 
tage that the pat has over the other forms is that curvature can 
readily be ascertained, but a mere curvature of the pat should 
not be considered as a failure in boiling unless accompanied by 
checking. The requirement sometimes given that a pat should 
not leave the glass in boiling is not reasonable, as a small amount 
of expansion may naturally be considered normal. 

The greatest difference in the methods of conducting the boil- 
ing test probably lies in the duration of the treatment, different 
specifications requiring the test to be made from one to as high 
as forty-eight hours. To determine the effect of different 
lengths of treatment a large number of tests on different cements 
were made by the author and the time at which failure occurred 
was observed. It was found that of those samples which did 
not pass the test, 22 per cent, failed in the first half hour, 57 per 
cent, failed in the first hour, 85 per cent, failed in two hours. 96 
per cent, in three hours, and 99 per cent, in four hours. Only i 
per cent, of the tests that failed developed this action in over 
four hours, although many of them were carried up to twen:y- 
four, and a few to forty-eight hours ; thus showing generaUy 
that a test piece of cement standing three or four hours of boiling 
will almost invariably stand a much greater length of time, and 
also that at least three or four hours should always be allowed 
for the test. 

The time allowed for the specimen to harden before it is 
tested may cause considerable differences in the results, but if it 
always be given time to fully develop hard set the differences 
will be slight. Pats of cement allowed more than about twelve 
hours to harden will, if unsound, fail when tested by boiling at 
almost any time in the future. The author has had normal 
pats as old as six months and apparently perfectly sound, which 
when put through the boiling test showed a failure almost identi- 
cal with that obtained on the original test six months previously. 



SOUNDNESS. lyi 

If, however, the specimen is tested before it has fully hardened, 
the differences obtained in the results are often very decided, 
and, curiously enough, may operate in either direction — that is 
to say, a pat of cement may fail more readily when one hour old 
than when twenty-four hours old, or a one-hour pat may pass 
the test, while the twenty-four-hour pat may fail. The reason 
for this action is by no means apparent, but it may be observed 
that, in the ordinary case of a cement high in free lime from 
underburning, the failure will usually be more marked in the 
fresher specimens, and that in the more infrequent case of a 
cem.ent normally burned, but high in lime by reason of ])OOr pro- 
portioning, the failure is often more marked in the older speci- 
mens. It would seem in this case that the cement was sufftcientl>' 
strong to retain coherence in the test although insufficiently 
hardened, and that in this condition the lime was capable of be- 
coming hydrated without causing disintegration. 

For the same reasons a treatment of the specimen in a bath, 
of steam before immersion in boiling water is generally less 
severe than if the specimen be boiled without this treatment, 
particularly so if the test be made before the test piece has be- 
come fully hardened. 

It is also evident from the foregoing that tests made in steam 
alone without subsecjuent immersion in hot or boiling water ma\ 
often give rise to erroneous conclusions regarding the results, 
especially if the specimens be tested soon after making. Tests 
made at temperatures ])elow 140^^ or 150^ h'ahr., also, are not 
sufficiently severe to serve as an indication of (juality, there 
being freciuent cases on record in which samples have withstood 
the 115° hot water test and yet have tailed in the normal i)ats in 
less than 28 days. 

Apparatus. — Mgure 94 shows an elaborate ft^rni of ai)i)araius 
used in the lMiila(leli)hia Laboratories for conchietin^ .ill hot 
water and steam tests. It consists of a double coi)i)er bo.x cov- 
ered with felt and asbestos. The inner tank contains two tiers 
of shelves of wire netting and is filled wjiii water to a point be- 
tween these tiers so that the test specimens may be either im- 
mersed or kept in the vapor above the water, wliicli is main- 
tained at a lixed heiglil l)\ means oi constant level bottles. Tlie 
space between the two bo.xes serves as a steam jacket into which 
the ste.'ini is introduced after passing thrtMigh a pressure regn- 



172 



PRACTICAL CEMENT TESTING. 



lator. The temperature is controlled by a Heintz steam thermo- 
regulator so that the water may be kept at any fixed tempera- 
ture for an indefinite time. For all but the largest laboratories, 
however, such an apparatus is unnecessarily elaborate. 

Figure 95 shows a much simpler form of hot water bath^ con- 
sisting of a double copper box, 18 ins. x 22 ins. x 18 ins., outside 
dimensions, and operating m manner exactly similar to that 
given before. The jacket, however, contains water, instead of 







^^^^^^'^^^^^^^^^^'^^^^^^^^^ 



1 



End Elevation 




Plan. 



^< - ?4-' 

//7s/ife Inner Tank, 

Cover- & Bracheis-Tinned 
5eo+ion . 



Fig. 94.— Apparatus for Accelerated Tests Used in the Philadelphia Laboratories. 

steam, the heat being furnished by one or more Bunsen burn- 
ers, the gas for which comes through a regulator, such as is 
shown in Fig. 96, and which is inserted in the vent at the top 
of the jacket. Excellent results may be obtained with this ap- 
paratus. 

For boiling tests the simple copper box (6 ins. x 10 ins. x 
7 ins.), shown in Fig. 97, is all that is necessary. A Bunsen 



SOUNDNESS. 



173 



burner furnishes the heat, and the screen of wire nettino^ an 
inch above the bottom prevents the specimens from coming 
in contact with it. For steam tests, an exactly similar box is 

n 



I^t.v«\«r-.-if.vsv.v— .-.— siv.-iivw.— I 




'\ 



Fig. 95. — Simple Apparatus for Hot Water Tests. 

used, except that the wire shelf is raised to a height of two 
inches above the water level. Any rough vessel may be used 
for occasional boiling tests, provided care is taken that the 
specimen does not come in contact with the bottom, 
and also that the evaporated water be replaced slow- 
ly, thus preventing a sudden chilling. Any perma- 
nently mounted apparatus for any of these tests 
should be provided with a constant level bottle as 
shown in Fig. 98, which is a large bottle pro- 
vided with an opening at the bottom, and having 
at the top a tightly fitting rubber cork thnnigh 
which passes a glass tube. If the bottom of 
the bottle be connected with the boiling appar- 
atus, the water will be maintained at a level 
equal to the height of the bottom of the glass 
rod. 

Tests Used by the Author. — From all sampKs of Portland 
cement the author makes two pats 3.} inches in diametor, '^-inch 
thick at the center on plates of glass (4 ins. \ 4 ins. \ J -in.), 
and also a small ball about i.| inches in diameter, which is shown 




Fig. 96. — 
Gas Regula- 
tor. 



174 



PRACTICAL CEMENT TESTING. 



in Figs. 80 and 81. These are made from neat cement paste 
of normal consistency, the material left over from the set test^"' 
being used for this purpose. They are marked as soon as made 
with a pointed piece of steel, and placed in the damp closet for 
24 hours. At the expiration of that time, one of the pats is 
placed in water at a temperature of 65 to 70 degrees Fahr., and 
the other put in a closet protected from dampness, heat and 
sun's rays. The tanks used for storing the water pats are simi- 
lar to those used for briquettes. f These two pats are examined 




Fig. 97. — Apparatus for Making Boiling Tests. 

at 7 days, 28 days, and thereafter at intervals of a month as 
long as they are kept, and their condition carefully recorded. 
The ball, as soon as it is removed from the damp closet, is 
placed in cold water in an apparatus similar to that shown 
in Fig. 97. The water is gradually (in about half an hour) 
raised to boiling, and maintained at that point for 3 hours, 
after which the specimens are removed and examined. Care 
must be taken to use fresh water ever} day, since, if repeatedly 
used, the water becomes strongly alkaline, sufficiently to often 
seriously afifect the results. 

♦See page 08. 
tSee page 1.34. 



SOUNDNESS. 



175 



Value of the Accelerated Tests. — Regarding the relation be- 
tween the accelerated tests and the other tests for soundness 
and strength, there is but little question that the results are 
more or less corroborative. The author has recently com- 
piled some data on this point covering over a thousand tests 
on many varieties of cement with the following results : 

Of all samples failing to pass the boiling test, 34 per cent, 
of them developed checking or curvature in the normal pats 
or a loss of strength in less than twenty-eight days. Of those 
samples that failed in the boiling test, but remained sound at 
twenty-eight days, 3 per cent, of the normal pats showed check- 
ing: or abnormal curvature in two months, 
7 per cent, in three months, 10 per cent, 
in four months, 26 per cent in six months, 
and 48 per cent, in one year ; and of these 
same samples, 37 per cent, showed a fall- 
ing off in tensile strength in two months, 
39 per cent, in three months, 52 per cent. 
in four months, 63 per cent, in six months, 
and 71 per cent, in one year. Or tak- 




FiG. 98.— Illustrating the Principle of the Constant Level Bottle. 

ing all these together, of all the samples that failed in the l)oil- 
ing test, 86 per cent, of them gave evidence in less than a year's 
time of possessing some injurious quafit). 

On the other hand, of those cements passing the boiling ust. 
but one-half of i per cent, gave signs of failure in the normal 
pat tests, and but 13 per cent, showed a falling ofT in stnMigtli 
in a year's time. 

To show roughly the relation in tensile strength ol tlu^sr 
cements failing and passing the l)oiling test, Table XTTI. was 
compiled from 200 nearly consecutive tests of a single iMand. 



176 



PRACTICAL CEMENT TESTING. 



/ Failing 

Neat 


in Test • 

1 : 3 Sand 


Passing Test « 

Neat 1 : 3 Sand 


530 




391 






817 


197 


643 




237 


749 


273 


727 




303 


713 


274 


732 




312 


702 


242 


749 




314 



100 of them failing in the test and loo passing. The high Hme 
in those samples failing to boil is easily apparent in the high 
value of the seven-day neat test and its subsequent retrogres- 
sion. While covering but a comparatively small number of 
tests, this table may, however, be considered fairly typical of 
the relations of strength to the accelerated tests, although ex- 
ceptions, of course, frequently occur. 



TABLE XLII.---Coraparison of the Tensile Strength of Briquettes Failing 

and Passing in the Boiling Test. 

(Tests by the Author.) 

Age 

1 day 

7 days 

28 " 

2 months 

3 " 



In order to show the great value sometimes obtained from 
the results of the boiling test, several examples are given in 
Table XLIII. of tests of cements occurrmg in the regular rou- 
tine work of the author's laboratory. The photographs of two 
of these tests are shown in Figs. 99 and 100. The first example 
is particularly remarkable in that at twenty-eight days there 
was absolutely no sign of failure whatsoever, except in the 
boiling test. All of these samples were normal in specific 
gravity, fineness, and time of setting, and both the tensile 
strength and the normal pats passed a good test at seven days, 
the boiling test giving the only indication of an unquestion- 
able failure occurring at a later period. It should also be 
stated that these are not exceptional or ''freak" cases, but ex- 
amples of a common, although not frequent, occurrence. 

Another point of considerable interest regarding the boiling 
test is this: The statement is often made that although a ce- 
ment • failing in this test may be otherwise sound, a cement 
passing the test may always be considered entirely safe, and 
while this is generally true, it is by no means an invariable rule. 
It occasionalh happens that a cement may pass the boiling 
test well, and yet check and disintegrate in the normal tests, 
particularly if the cement be slow setting, high in lime, and the 
test made soon after the specimen is moulded. In these cases 



SOUNDNESS, 



177 



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178 



PRACTICAL CEMEXT TESTING. 




Briquette 

Kept iu 
Water. 




Normal 
Air Pat. 



Normal 
Water Pat. 



Fig 99. — Examples of Un- 
soundness Indicated by 
the Boiling Test. (See 
Table XLIII, Nc. i.) 
Photographed at Four 
Months. 




SOUNDNESS. 



179 



Briquette 
Kept in 
Water. 




Fig. kk). — Examples 
of Unsoumlness Indi- 
cated by the I3oiliiij» 
Test. (See Table 
XLlll.No. 2.) rho- 
tOkiraplu'd a t l'"our 
Months. 



l8o PRACTICAL CEME::7 7ZSTIXG. 

it seems that the boiling at tirst rends to hydrate the lime and 
render it inert, although it would be active under normal con- 
ditions. It thus may be possible to add small quantities of lime 
to a sound cement and treat it in such a way that it will pass 
the boiling test perfectly, and yet fail under normal conditions. 
The author has seen the photograph of a test made in which as 
much as 15 per cent, of lime was added to a cement, and boiled, 
with excellent results, although the normal pats failed in a 
ver\- short time. 

Although it has been shown, however, that the results of the 
accelerated tests generally corroborate the other laboratory- 
tests, it, nevertheless, cannot be denied that, in the vast ma- 
jority of cases, work done with cement determined in' the lab- 
orator}* by means of the boiling test to be unsound will grive 



TABLE XLIV. — Examples of Retrogression in the Strength of Neat 
Briquettes, Without Similar Action in those of Sand Mortar. 

(Tests bv the Author.) 



Iday 


- ::..T. 


2^ livi 


4=11- 


1 yi'--.T 


7 days 


iSdays 


-Lmos. 


1 v^sr 


450 


"^2 


- ; 


; -.2 


2C3 


iSo 


2^2 


309 


;i-t 


493 


7»7 


801 


317 


241 


172 


247 


2S3 


297 


429 


685 


793 


593 


318 


200 


251 


20S 


323 


475 


791 


790 


;o2 


291 


102 


267 


287 


301 


502 


823 


752 


421 


200 


1S4 


229 


252 


251 


423 


802 


741 


5-1 


277 


212 


237 


290 


303 


479 


784 


782 


520 


321 


202 


238 


301 


318 


401 


TQI 


797 


J.03 


200 


17* 


251 


277 


276 



most excellent results in practice, and show not the renioiest 
sign of any sort of failure. 

One reason that most cemen: shows such a radical differ- 
ence in the results of the laborator}- and in actual use is the 
fact that almost invariably the test is made considerably be- 
fore the cement is used, a week almost always elapsing and 
often as much as a month, thus giving it plenty of time to 
season, and render the expansive elements ineffective, the short- 
est time customarily allowed, that of one week, being ver\- often 
sufficient to make the difference between a radically unsound 
cement and one which is normal. 

Another reason is that the disintegrating action of a cement 
is always far greater when mixed neat than when mixed with 
an asrsrresrate. and the srreater the amount of the asr^resrate the 



SOUXDXESS. l8i 

less the tendency to unsoundness. This can often be observed 
in the laboratory tests, cements often completely disintegrat- 
ing in the neat briquettes, but retaining their strength in the 
sand tests. Table XLIV. shows a few instances of this sort. 
(See also Fig. loi.). 

Even eliminating these two conditions, however, many cases 
are on record in which failure in boihng has not been cor- 
roborated by failure in the work, even though the cement was 
used at once and in a rich mixture, showing that even when 
the conditions of testing and actual work are most nearly alike, 
the indications of the accelerated tests are by no means 
infallible. 

Concerning the value of the boiling test, the Report''' of 
the Board of Engineer Officers (U. S. A.) says : "Of all these 
tests the boiling test is the simplest, requires only apparatus 
everywhere available, and is recommended by the Board. It 
has been the experience that this test detects material that is 
unsound by reason of the presence of active expansives ; but 
in some cases it rejects material that would give satisfactory 
results in actual work and will reject material that would stand 
this test after air slaking.'' 

*'The great value of the test lies in its short-time indications 
and in at once directing attention to weak points in the cement 
to be further observed or guarded against. Of two or more 
cements offered for use or on hand, the cements that stand the 
boiling tests are to be taken preferably ; it should be constant- 
ly applied on the work among other simple tests to be noted, 
for although the boiling test sometimes rejects suitable ma- 
terial, it is believed that it will always reject a material un- 
sound by reason of the existence of active expansives. Sul- 
phate of lime, while enabling cements to pass the boiling tests, 
introduces an element of danger." 

"This test is proposed as suggestive or discriminative only. 
Except for works of unusual importance it is not roconunendcd 
that a cement ])assing the other tests proposed shall bo rejected 
on the boiling test." 

A committee of the Society of German Portland Cement 
Manufacturers has reported: "After having made tests for 
the length of two years, the Commission Hociding as to the 

♦Professional papers, No.28, Corps of Engiucor-, V. 9. A. 



l82 



PRACTICAL CEMENT TESTING. 



Constancy of Volume and the Adhesive Power of Portland 
Cement came to the conclusion that none of the so-called ac- 
celerated tests, boiling tests, etc., was capable of afifording in 



..■^- 











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3 g 




go 

n CI 

.?o 
£ g 

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:? '-' 






.2" 



all cases a quick and reliable judgment in regard to the prac- 
tical usefulness of a cement." 

The Committee of the American Society of Civil Engineers* 
says: "In the present state of our knowledge it cannot be 



■s'ee Appendix A. 



SOUNDNESS. 183 

said that cement should necessarily be condemned simply for 
failure to pass the accelerated tests ; nor can a cement be con- 
sidered entirely satisfactory, simply because it has passed 
these tests." 

Interpretation of Results. — To properly interpret the results 
of the soundness tests requires large and varied experience, and 
is undoubtedly the most difficult phase of the testing of cement. 

Although not infallible, it is safe to consider the results 
of the normal tests, assuming correct manipulation, as abso- 
lute criteria of quality, and to reject all samples that fail to 
pass them. 

If a sample fails in the accelerated test, as typified by the 
boiling test, it is the safe course to hold the shipment for at 
least 28 days, and then to make a second determination upon 
a fresh sample. If this second sample passes the test, it shows 
that the additional seasoning has made the shipment entirely 
sound and fit for use. If the second sample fails, and the neat 
tensile strength shows any decided retrogression in 28 days, 
the shipment should be considered as suspicious and probabh 
unsafe, at least for the important parts of a structure. Gen- 
erally, however, if all the other physical requirements are sat- 
isfied, and the boiling test alone fails, it is neither advantageous 
nor justifiable to reject the shipment, except, possibly, in a com- 
petitive test, in which case the samples passing the boiling test 
are to be considered preferable. 



CHAPTER XL 

CHE^IICAL ANALYSIS. 

Components. — The components of Portland cement whose 
amounts are usually determined by chemical analysis are : — 
silica (SiOo), alumina (ALO3), iron (Fe203), lime (CaO), mag- 
nesia (]\IgO), and sulphuric acid (SO3). Other ingredients 
less frequently determined are : — carbonic acid (COo), water 
(HoO), alkalies (XaoO + KoO), and sulphur (S). In practice, 
alumina and iron are often determxined together (written as 
R2O3), and carbonic acid and water together as ''loss on igni- 
tion." The average amounts of these ingredients, together 
with a table of typical analyses have already been given in 
Chapter 11. 

Significance. — \Miile chemical analysis plays a most impor- 
tant role in controlling the product in cement manufacture, it 
has comparatively small value in the testing of the finished 
material. This is due to the fact that the quality of the product 
depends not only upon the proportions of the different ingredi- 
ents, but also upon their arrangement or the form of combina- 
tion in which they exist. Thus it may happen that the content 
of lime, silica and alumina in a cement may be perfectly nor- • 
mal, and yet, by reason of defects in the process of manufacture, 
the material be of decidedly faulty character. For the detec- 
tion of adulterants, or to determine whether certain constitu- 
ents are present in amounts exceeding that believed to be safe, 
chemical analysis is of considerable value. 

Analyses for silica, iron, alumina and lime are made in con- 
trolling the manufacture, but give little information in regard 
to the quality of the finished product, unless their proportions 
are grossly incorrect. Regarding this point the Committee of 
the American Society of Civil Engineers says :* "Faulty char- 
acter of cement results more frequently from imperfect prep- 
aration of the raw material or defective burning, than from in- 
correct proportions of the constituents. Cement made from 
very finely ground material, and thoroughly burned, may con- 
tain much more lime than the amount usually present and still 
be perfectly sound. On the other hand, cements low in lime 

♦See Appendix A. 



CHEMICAL ANALYSIS. 185 

may, on account of careless preparation of the raw material, 
be of dangerous character. Further, the ash of the fuel used in 
burning may so greatly modify the composition of the product 
as largely to destroy the significance of the results of analysis." 

Determinations of magnesia, sulphuric acid, sulphur, alka- 
lies, and carbonic acid are made to ascertain whether these 
ingredients are present in inadmissible quantities. Best Ameri- 
can practice in specifications limits magnesia to 4% and sul- 
phuric acid to 1.75%. 

In the following description of methods of chemical analy- 
sis, it is assumed that the reader has an elementary theoretical 
knowledge of chemistry, and is familiar with the ordinary 
processes of manipulation of chemical apparatus. No engineer, 
however well informed, should ever attempt chemical analy- 
sis without either a course of study in college, or a practical 
apprenticeship in some laboratory, for, unless he does so, it is 
impossible to obtain results of even approximate accuracy. 

Methods of Analysis. — The general method given here for 
the analysis of Portland cement is in all essential particulars 
an elaboration of the method* proposed by the Committee on 
Uniformity in the Analysis of the Materials for the Portland Ce- 
ment Industry of the New York Section of the Society for 
Chemical Industry, and which was indorsed! by the Committee 
on Uniform Tests of Cement of the American Society of Civil 
Engineers. This method is supposed to give the greatest ac- 
curacy consistent with a fair amount of rapidity, and, while 
scarcely practicable for control work on account of the many 
corrections, gives just about the degree of accuracy that should 
be obtained in an experimental laboratory. Following the 
system for general analysis are alternatiye methods that will 
enable the operator to secure greater refinement or greater 
rapidity as may be desired, and also short-cut methods suit- 
able for control work. 

GENERAL METHOD FOR THE ANALYSIS OF PORTLAND CE- 
MENT, LIMESTONE AND RAW MATERIAL MIXTURES. 

The sample should first be find}- ground in an agate mortar. 
and a sufficient quantity for all determinations preserved in ? 
tightly stoppered bottle. 

*See Ai)i)eiulix W. 
tSeo Appendix A. 



i86 PRACTICAL CEMENT TESTING. 

Loss on Ignition. — 0.5 gram of the sample is placed In a 
weighed platinum crucible and ignited, over a blast lamp, to 
constant weight. The crucible should be covered and the flame 
applied to the bottom at an angle of 45°. Ten minutes over 
a good blast should be sufficient for a cement and about 20 
minutes for a limestone or slurry. The weight should be 
checked by 5 minutes further blasting. 

Silica. — Having determined the loss, the ignited residue is 
transferred to a casserole and digested on a warm plate with 
20 c. c. hydrochloric acid (i — i), until completely dissolved, 
the casserole being covered with a watch glass. The ignited 
cement or slurry should be entirely soluble in dilute acid; the 
presence of any gritty particles which can be felt with a stirring 
rod is an indication of incomplete solution. In such cases, 
these particles should be filtered off, the filter and contents be- 
ing ignited in a platinum crucible. The residue should then be 
fused with a small quantity of sodium carbonate, the fusion 
taken up with hot water and added to the main solution, which 
is then evaporated to hard dryness. The residue Is digested, 
for about 5 minutes, with 15 c. c. hydrochloric acid, after which 
the solution is made up to 100 c. c. with hot water. The sepa- 
rated silica is filtered off on an ashless filter and well washed 
with hot water, the filtrate and washings being caught In a sec- 
ond casserole. The filtrate Is again taken to dryness, the 
residue treated exactly as before, and the small second precipi- 
tate of silica filtered off on a second filter. The two precipi- 
tates of silica are burned together m a weighed platinum cru- 
cible, first over the Bunsen burner until the carbonaceous mat- 
ter is destroyed, and then over the blast for 15 minutes, after 
which it is cooled and weighed. Its weight should be checked 
by 10 minutes further blasting. 

Silica almost invariably carries with It very small percentages 
of other constituents — usually Iron and alumina. But as Iron 
and alumina commonly contain small percentages of sIHca, 
which have not been removed by evaporation with hydrochloric 
acid, the errors practically counterbalance one another and, for 
ordinary purposes, a correction Is not necessary. One con- 
stituent, moreover, should not be corrected without also cor- 
recting the others. 

To determine the amount of impurity In the silica, it Is mois- 



CHEMICAL ANALYSIS. 



187 



tened, after weighing, with a couple of drops of sulphuric acid, 
after which the crucible is filled about ^ full with hydrofluoric 
acid and left on the hot plate until the contents have evaporated 
to dryness. The crucible is then carefully heated to redness, 
after which it is blasted for a few minutes, cooled and weighed. 
The loss in vv^eight is pure silica — (Si02). 

The residue is added to the iron and alumina. It is advis- 
able to use the crucible containing the residue from the silica 
correction for the ignition of the iron and alumina precipitate. 

Iron and Alumina.— To the filtrate from the silica, which 
should be made up to about 250 c. c, a very slight excess of 
ammonia is added; the solution is boiled to expel the excess 
of ammonia, after which the precipitate is allowed to settle. 
The solutioxi should be filtered, while hot, into a large beaker, 
and the precipitate washed a couple of times with hot water. The 
funnel containing the iron and alumina is inverted and the pre- 
cipitate carefully washed back into the original beaker with 
a spray of hot water. It is dissolved in hydrochloric acid, the 
solution diluted to 250 c. c. and the iron and alumina again 
precipitated with ammonia. The precipitate is then brought 
on the same filter and is thoroughly washed as before, the 
filtrate and washing being united with the first filtrate. In 
washing the gelatinous precipitate, the stream from the wash 
bottle should be so applied as to completely break up the mass 
each time and wash it free from the paper. 

The precipitate and filter are transferred to a weighed plat- 
inum crucible, carefully ignited over a Bunsen flame until all 
the paper is buraed of¥, after which it should be blasted for 
5 minutes, cooled and weighed. The weighed residue is iron 
and alumina (Fe^Og + ALO3). 

Iron Oxide. — The crucible containing the weighed oxides of 
iron and alumina is half filled with potassium bisulphatc, cov- 
ered and placed over a low Bunsen flame which is gradually 
raised as fusion proceeds. When fusion is complete and no 
more dark particles are floating about, the crucible is removed 
from the flame, manipulated so that the fusion runs up the 
sides, and cooled. When cold, the fused mass is transferred 
to a casserole, any adhering particles being washed out with 
hot water; 50 c. c. should l)e sufticient for solution of the fu- 
sion. Five c. c. concentrated sulpluuic acid are addetl. and the 



i88 



PRACTICAL CEMENT TESTING. 



solution is evaporated until fumes of SO3 are evolved. It Is 
allowed to cool, diluted with water to 50 c. c. and filtered from 
the separated silica, which is ignited, weighed, and its weight 
added to the original silica. 

The solution, made up to 150 c. c, is placed in a flask and 
reduced, while hot, by hydrogen sulphide. The flask is then 
connected with a carbonic acid generator, and the excess 
of hydrogen sulphide boiled off in an atmosphere of carbon 
dioxide. Any separated sulphides are filtered off, after which 
the iron may be determined by titration with 
standard potassium permanganate. 

Some operators prefer reducing the solution 
with zinc ; but in this case titanium is also re- 
duced and determined with the iron, a diffi- 
culty which is obviated by reduction with 
hydrogen sulphide. The titanium may be 
determined colorimetrically after the titra- 
tion.* 

In making the reduction with zinc, the 
Jones reductor ( Fig. 102 ) is the most con- 
venient form of apparatus. The tube, having 
a small plug of mineral wool at the bottom, 
is filled to within a couple of inches of the 
top wdth pure shot zinc. To start the appara- 
tus, the main tube containing the zinc is filled 
with 5% sulphuric acid, with the stop-cock 
open. When a good reaction has started, the 
Fig. 102— The Jones solution of the bisulphate fusion is poured into 
Reductor. the funnel, which should then be covered with 

a watch glass. Suction is applied at once to the flask, and 
the tube is kept filled, if necessary, by occasionally loosening 
the stopper at the top of the tube. The solution is never al- 
lowed to fall below the top of the zinc, and the level should be 
kept up by continual additions of water, being careful to rinse 
off the watch glass and the vessel which contained the solu- 
tion. When all reaction in the tube ceases, the suction flask is 
disconnected, brought to the burette containing standard per- 
manganate and the iron titrated. 

Before beginning any determinations, blanks of acid and 

♦W. F. Hillebrand, Bulletin No. 176. U. S. Geological Survey. 




CHEMICAL ANALYSIS. 189 

water should be run through the reductor exactly as in mak- 
ing a determination, and titrated with permanganate until the 
amount required is found to be constant — about o.i to 0.2 c. c. 
This must be deducted from the amount required in analysis. 

The permanganate solution may be standardized against iron 
wire, and should be made at least 24 hours before standardiz- 
ing and kept in dark bottles. Two grams per liter is a good 
strength. 

For standardizing, 0.2 gram of piano wire, having been pol- 
ished with emery cloth and carefully cleaned, is made into a 
small coil and accurately weighed. In a 4 oz. Erlenmeyer 
flask provided with a valve stopper, 40 c. c. of i — 3 sulphuric 
acid are heated to boiling; the coil of wire is then dropped 
in, and the stopper quickly inserted with the valve open. When 
the wire has completely dissolved the solution is boiled for a 
couple of minutes, after which it is allowed to cool with the 
valve closed. When cold, the solution is transferred to a 
beaker, and the flask washed out a couple of times with cold 
water. Permanganate is then run into the solution from a 
burette until the pink color appears. 

The weight of wire taken (less 0.3% for impurities) divided 
by the number of c. c. of permanganate equals the strength of 
the solution per c. c. in terms of iron. This result divided by 
0,7 equals its strength in terms of Fe^Oa. 

Lime. — The combined filtrate and washings from the iron and 
alumina — about 500 c. c. — are brought to a stroiig boil on a 
hot plate, and, while boiling, there are added 25 c. c. of a hot 
saturated solution of ammonium oxalate. Boiling is continued 
for 5 minutes, after which the beaker is set aside in a warm 
place. When the precipitate has completely settled — which 
should be in about 20 minutes — the solution is filtered int(^ a 
large beaker, the precipitate being brought on the filter paper 
and washed a couple of times with hot water. The funnel is 
then inverted and the precipitate washed back into the original 
beaker. The precipitate is dissolved in hych-ocliloric aci^l, ami 
the solution diluted to 300 c. c. Five c. c. ammonium oxalate 
are added, the solution brought to a strong boil, after which 
ammonia is carefully added until the solution smells strongly 
of it. After boiling for 5 minutes, the beaker is set aside, and, 
when tlie precii)itate has complelel) settled, it i> oc^lloctetl on 



igo PRACTICAL CEMENT TESTING. 

the same filter as before, washed several times with hot water^ 
the filtrate and washings being united with those from the first 
precipitation. 

The precipitate is dried by placing the funnel in an oven or 
supporting it over a hot plate. When dry, it is carefully brushed 
on a piece of black glazed paper, and the filter paper ignited 
in a weighed platinum crucible. When all the carbonaceous 
matter has burned off, the remainder of the precipitate is trans- 
ferred to the crucible and the whole ignited to constant weight 
over a strong blast. With the crucible covered, twenty minutes 
over a good blast are usually suiBcient. The crucible should 
be weighed as soon as cold. The final weight gives lime — CaO. 

In precipitating the calcium oxalate, the solution should be 
strongly boiling before any attempt at precipitation is made, 
otherwise there will not be sufficient ebullition to keep the 
precipitate in suspension and the beaker will bump and likely 
break. 

Magnesia. — The combined filtrate from the lime precipita- 
tion, after boiling for a few minutes to make sure that no more 
• calcium oxalate comes down, is acidified with hydrochloric acid 
and evaporated on a hot plate to about 200 c. c. when 20 c. c. 
of a freshly prepared solution of microcosmic salt are added 
and the solution boiled for abtout 5 minutes longer. It is then 
transferred to a smaller beaker of suitable size and cooled by plac- 
ing the beaker in a tray of ice water. When perfectly cool, 
ammonia is added a few drops at a time, with constant 
stirring, until the precipitate of magnesium ammonium phos- 
phate is formed. A slight excess of ammonia is then added 
and the beaker set aside over night. The precipitate is filtered 
ofif and thoroughly washed with a solution of i — 4 ammonia. 
It is dried and ignited in a platinum crucible, first over a Bun- 
sen burner, until most of the carbon is burned off, and then 
over a strong blast until perfectly white, being well broken 
up with a platinum rod. The ignited residue is magnesium 
pyrophosphate— ]\Ig,.P,,07. Its weight multiplied by .362 gives 
the weight of magnesia — MgO. 

jll^The Mg,P,,0- should be completely soluble in hot hydro- 
chloric acid, but is likely to contain amounts of silica depend- 
ent on the quality of the glassware used for evaporating. In 
this event, the silica is filtered off, the filtrate and washings. 



CHEMICAL ANALYSIS. 191 

caught in a small beaker and diluted to 100 c. c. Three c. c. 
of saturated microcosmic salt solution are added and the mag- 
nesium ammonium phosphate reprecipitated by the addition of 
ammonia and treated in the manner previously described. 

Sulphuric Acid. — For this determination a separate sample 
of 0.7 gram is taken and digested on a warm plate with 50 
c. c. of I — 4 hydrochloric acid until nothing remains in suspen- 
sion other than a few particles of flocculent insoluble silicious 
matter. This is filtered oft', the filtrate and washings made up 
to about 200 c. c. and brought to boiling. Ten c. c. of a hot 
10% solution of barium chloride are then added, with brisk 
stirring, and the boiling continued for 5 minutes, after which 
the covered beaker is set aside for several hours on a warm 
plate — about 50° C. When the precipitate has completely set- 
tled, it is filtered on a small paper, washed several times with 
hot water and then carefully ignited, with the filter, in a 
weighed platinum crucible over a Bunsen flame until perfectly 
white. This weighed precipitate is barium sulphate — BaS04 — 
multiplied by .343 gives the wxight of sulphuric anhy- 
dride — SO3. 

Allowing the precipitate to settle out in a warm solution has 
been found advisable, since it is then easily retained by the 
filter ; otherwise it is apt to run through and give consider- 
able trouble. 

ANALYSIS OF CEMENT ROCK, CLAY AND NATURAL 

CEMENT. 

In cases where the substance is not decomposible by hy- 
drochloric acid, recourse must be made to fusion with smliuni 
carbonate. A 0.5 gram sample, after the loss on ignition has 
been determined, is intimately mixed with about 10 times its 
weight of sodium carbonate, with which a few small crystals 
of potassium nitrate have been ground. Hie mixture is trans- 
ferred to a platinum cruci])le with a tight fitting cover and 
heated over a strong flame until it is in a state of (|uiet fu- 
sion. A few minutes over the blast lain]) is advisable before 
cooling. The fusion is then run up the sides of the crucil)le,4l 
and allowed to cool, after which the crucible, with its content!* 
and the lid, are placed in a casserole, covered witli water and 
allowed to (hgesl on a hot plate until the fusion is well ilisin- 



1^2 PRACTICAL CEMEXT TESTING. 

tegrated. The crucible and lid are then removed, washed, using 
h\drochloric acid if necessary, and sufficient hydrochloric acid 
is carefully added to bring everything into solution. The 
solution is then evaporated to dryness for the separation of 
silica, after which the procedure is exactly similar to that used 
for Portland cement and limestones. The precipitates, how- 
ever, all require considerably more washing owing to the fixed 
alkali from the fusion which is difficult to wash out. The in- 
experienced operator should test a few drops of the washings 
with silver nitrate — a precipitate of silver chloride indicates that 
the washing has been insufficient. 

ALTERNATIVE AND ADDITIONAL METHODS. 

Lime — Volumetric Method. — In mill laboratories and where 
greater rapidity is necessary, the lime generally is determined 
volumetrically. The method depends on the following reaction: 
5 HXoO, + 2 K MnO, - 3 H,SO, = 

K.SO, ^ 2 MnSO, + 8 H.O -f 10 COo. 

Six grams per liter is a convenient strength for the perman- 
ganate solution. It should be made not less than 24 hours — 
preferably several days — before standardizing, should frequent- 
ly be well shaken during that period and kept in dark bottles. 
It may be standardized against oxalic acid. The acid, how- 
ever, should be recrystallized, dried between filter paper and 
finally in a current of dry air, and preserved in a tightly stop- 
pered bottle. 0.2 gram of the cr} stals so prepared is dissolved 
in LOO c. c. of water ; 5 c. c. concentrated sulphuric acid are 
added and the solution bTought just to a boil. The perman- 
ganate solution is then run in from a burette until the pink 
color is permanent. The weight of acid taken divided by the 
number of c. c. permanganate solution used gives the value of 
the solution in terms of oxaHc acid. This result multipUed by 
0444 gives the value in terms of CaO. Duplicate determina- 
tions should not vary more than 0.00002. 

When pure calcite (CaCOg) can be obtained, it is preferable 
to dissolve a weighed quantity, precipitate the lime by am- 
monium oxalate, and standardize the solution against it as in 
the regular course of analysis. 

For the determination of the lime, the precipitate of cal- 
cium oxalate is obtained as for the gravimetric method. It is 



1 



CHEMICAL ANALYSIS. 193 

washed five or six times with hot water, or until a few drops 
of the washings fail to decolorize a similar quantity of dilute 
permanganate. The funnel is then inverted and the precipitate 
washed back into the original beaker, after which the filter 
paper is spread out on the inner side of the beaker, and washed 
with I — 4 sulphuric acid to dissolve any adhering particles of 
precipitate, followed by hot water. The precipitate in the 
^beaker is then stirred with a spray of the i — 4 sulphuric acid 
until solution takes place. 

It is diluted to 200 c. c, brought barely to a boil, and titrated 
with standard permanganate. The number of c. c. taken mul- 
tipHed by the CaO value gives the amount of lime. 

Magnesia — Volumetric Method. — The simplest method depends 
on the following reaction : 

Mg (NH,) PO, + H.SO4 = (NHJ H0PO4 + MgSO,. 

The filtrate from the lime precipitate having been consider- 
ably reduced in volume by evaporation, is transferred to a 
large Erlenme}er flask and made strongly ammoniacal. 20 
c. c. of a saturated solution of microcosmic salt are then added 
and the mixture is thoroughly shaken until the precipitate is 
well formed. The precipitate is allowed to settle, filtered out" 
and washed as usual. The paper is then spread out on a bisque 
plate. This will rapidly absorb the greater part of the water 
and ammonia, after which the paper is removed from the plate 
and dried in an oven at 50° or 60° C, for fifteen minutes. 
When this is accomplished, the paper and precipHate are thrown 

into a beaker and an excess of — sulphuric acid added. When 

10 

the precipitate has entirely dissolved, the excess of acid is 

N 
titrated back with — ammonia. 
10 

I c. c. -- H..SO, = .002 Mg:0. 
10 " 

Mr. R. K. Meade* has evolved a method, briefly doscrihod 
by Suttonf as follows: "When a solutit^n of arsoiiic acid con- 
tains suflicicnt sulphuric or hydrochloric acid, the arsenic is 
quickly reduced to arscnious acid even in the cold. For every 

'"Examination of Portland Cement." by R. K. Meade. 
.t"Volun3etrlc Analysis," by Francis Sutton. 



IC)4 PRACTICAL CEMENT TESTING. 

molecule of arsenic acid so reduced there corresponds two 
atoms of magnesium, two molecules or four atoms of iodine 
are liberated. This latter is titrated with sodium thiosulphate, 
and from the volume of standard solution required, the mag- 
nesium calculated. 

"The standard solutions are conveniently made as follows : 

"Standard sodium arsenate is prepared by dissolving 12.29 
grams of pure arsenious acid in nitric acid, evaporating on a 
water-bath to dr3.ness, neutralizing with sodium carbonate in 
solution, and when dissolved made up to a liter wdth distilled 
water. Each c. c. = 0.005 S^- o^ MgO. 

"The standard solution of sodium thiosulphate is made to 
correspond to this either by direct titration, or by making it 
equal to a standard iodine solution made by dissolving 52.24 
gm. of pure iodine, and 75 gm. of potassium iodide in about 
200 c. c. of water, and making up to one liter. Each c. c. = 
0.005 S^- ^^gO- 

"Process. — Pour the magnesia solution, which should not con- 
tain too great an excess of ammonium chloride or oxalate into 
an Erlenmeyer flask or a gas bottle of sufficient size. Add 
one-third the volume of the solution of strong ammonia and 
50 c. c. of sodium arsenate. Cork up tightly and shake vigor- 
ously for ten minutes. Allow the precipitate to settle some- 
what, then filter and wash with a mixture of water and strong 
ammonia (3 — i) until the w^ashings cease to react for arsenic; 
avoid, however, using an excess 01 the w^ashing fluid. Dis- 
solve the precipitate in dilute hydrochloric acid (i — i), allowing 
the acid solution to run into the flask in which the precipitation 
was made, and w^ash the filter paper with the dilute acid, until 
the washings and solution measure 80 or 100 c. c. Cool, and 
add from 3 to 5 gm. of potassium iodide, free from iodate; 
allow the solution to stand a few minutes, and then run in the 
standard thiosulphate until the color of the liberated iodine 
fades to a pale straw color. Add starch, and titrate until the 
blue color of the iodide of starch is discharged. If preferred, 
an excess of thiosulphate may be added, then starch and stand- 
ard iodine until the blue color is produced. On adding the 
iodide of potassium to the acid solution, a brown precipitate 
forms, which, however, dissolves when the thiosulphate is 
added. 



CHEMICAL ANALYSIS. 



195 






''Experience has proved that the whole process can be done 
within an hour, and the results are very near those given by 
gravimetric methods." 

Sulphuric Acid. — Mr. D. D. Jackson has devised'^' a photo- 
metric method for this constituent depending upon the tur- 
bidity of a solution holding barium sulphate in suspension. The 
cement is dissolved as in the regular method of determination, 
and the solution transferred to a 100 c. c. Nessler tube. When 
cold, crystals of barium chloride are added, after 
which the tubes are corked, well shaken, and set 
aside for a short time. 

For the determination there is a tube g-radua- 
ted into millimeters and inclosed in an opaque 
sleeve to shut out the light. Fig. 103. It is sus- 
pended in a rack so that the bottom is 3 inches 
above the flame of a standard candle ; and on 
looking down through the tube there is visible a 
bright circle of light. 

To make the determination, the precipitated 
solution in the Nessler jar is made up to the 
100 c. c. mark and thoroughly agitated. Suffi- 
cient of it is then slowly poured into the gradua- 
ted tube until the last addition just shuts out the 
circle of light at the bottom of the tube. This 
point is very well defined. For the number of 
millimeters of solution required, a table prepared 
by ^Ir. Jackson gives the corresponding amount 
Fig. 103. — Jackson's of sulphuric acid. 
Apparatus for De- While the method cannot be called an exact 
termining Sulphur- ^j^^, the results are accurate enough for ordinarv 
ic Acid. , , , 1 • , 

purposes, and the method is convenient where 

a great number of determinations are required. 

Total Sulphur. — Sulphur in clay and rock usually exists as 
iron pyrites, FeS.. For its determination, i gram of the fine- 
ly pulverized sample is intimately mixed with alxnit ton times 
its weight of a mixture of 10 i)arts soilium carbonate and i 
part potassium nitrate. The mixture is transferred to a tiglitly 
covered platinum crucible and heated to (luiet fusion over a 
strong P>unsen flame. It is advisable to have the crucible 

•Journal American rhomlcal Socioty. Vol. XXllI . N'o. 2. 




T96 PRACTICAL C EM EXT TESTIXG. 

placed in a hole through an asbestos board, in order that the 
gas from the flame ma\ not contaminate the fusion. 

The fusion is treated exactly as for the complete analysis 
of cement rock, etc., excepting hat when it has gone into solu- 
tion upon the addition of hydrochloric acid, the solution is 
filtered into a beaker of suitable size, brought to a strong boil, 
and the sulphur (now oxidized to sulphate) precipitated, while 

TABLE XLV. — For the Reduction of Observations Made "With Jackson's 

Sulphate Apparatus. 

(Compiled by Mr. Jackson.) 



Depth 


Per Cent. 


Depth 


Per Cent. 


Depth 


Per Cent. 


Depth 


Per Cent. 


Cm. 


SOs. 


Cm. 


SO3. 


Cm. 


SO3. 


Cm. 


SO3. 


I.O 


52 


4.0 


1-4 


7.0 


0.8 


lO.O 


0.6 


I.I 


4.8 


41 


1-4 


71 


0.8 


10.2 


0.6 


J. 2 


44 


42 


1-3 


7.2 


0.8 


10.4 


0.6 


I 3 


4 I 


4-3 


1-3 


7-3 


0.8 


10.6 


0-5 


1-4 


3-8 


4-4 


1-3 


7-4 


0.8 


10.8 


05 


1-5 


3-6 


4.5 


1.3 


7-5 


0.8 


II. 


0.5 


1.6 


3-4 


4.6 


1.2 


7.6 


0.8 


II. 2 


0.5 


I 7 


3-2 


4.7 


1.2 


7-7 


0.7 


II. 4 


0.5 


1.8 


30 


4.8 


1.2 


7-8 


0.7 


II. 6 


0-5 


19 


2.9 


4-9 


1.2 


7-9 


0.7 


II. 8 


0.5 


2 o 


2.7 


5-0 


II 


8.0 


0.7 


12.0 


0.5 


2.1 


2.6 


5-i 


I.I 


8.1 


0.7 


12.2 


0-5 


2 2 


2 5 


52 


I.I 


8.2 


0.7 


12.4 


o-S 


23 


2.4 


5-3 


I.I 


8.3 


0.7 


12.6 


0.5 


2.4 


2-3 


5-4 


1.0 


8.4 


0.7 


12.8 


0.4 


2 5 


2.2 


5-5 


1.0 


8.5 


0.7 


13.0 


0.4 


2.6 


2.1 


5-6 


1.0 


8.6 


0.7 


13-5 


0.4 


2.7 


2.1 


5-7 


1.0 


8.7 


0.7 


14.0 


0.4 


2.8 


2.0 


5.8 


1.0 


8.8 


0.6 


14.5 


0.4 


2.9 


1.9 


5-9 


1.0 


8.9 


0.6 


15.0 


0.4 


3-0 


1-9 


6.0 


0.9 


9.0 


0.6 


15-5 


0.4 


3-1 


1.8 


6.1 


0.9 


9.1 


0.6 


16.0 


0.4 


3-2 


1-7 


6.2 


0.9 


9.2 


0.6 


16.5 


0.4 


3-3 


1-7 


6.3 


0.9 


9-3 


0.6 


17.0 


0.3 


3-4 


1.6 


6.4 


0.9 


94 


0.6 


17-5 


0-3 


3-5 


1.6 


6.5 


0.9 


9-5 


0.6 


18.0 


0.3 


3.6 


1.6 


6.6 


0.9 


9.6 


0.6 


18. 5 


0-3 


3-7 


15 


6.7 


0.8 


9-7 


0.6 


19.0 


03 


3-S 


1-5 


6.8 


0.8 


9.8 


0.6 


19-5 


03 


3-9 


1.4 


6.9 


0.8 


9.9 


0.6 


20.0 


0-3 



boiling, with 10 c. c. of 10% barium chloride solution. After 
boiling 5 minutes longer, the beaker is set aside in a warm 
place. When the precipitate has completely settled it is filtered 
off, ignited and weighed. 

The weight multiplied by .258 gives the amount of iron py- 
rites FeS.. However, any sulpha i:e sulphur, determinable by 
the method of solution in hydrochloric acid, should have its 



CHEMICAL ANALYSIS. 



197 



corresponding weight of barium sulphate subtracted from the 
above, weight before multiplying by the factor. 

Sulphur (as Calcium Sulphide). — While this determination is 
not frequently made, it is sometimes desirable, especially with 
slag cements. Five grams of the sample are introduced into 
a 6-ounce Erlenmeyer flask, provided with a rubber stopper, 
having a small tap funnel and a delivery tube leading to the 
bottofn of an 8-inch test tube. The test tube is f filled with an 
ammoniacal solution of cadmium chloride ; 50 c. c. of i — i 
hydrochloric acid are run into the Erlenmeyer flask through 
the tap funnel, the solution gradually heated to boiling and 
boiled for several minutes. The hydrogen sulphide evolved 
precipitates cadmium sulphide in the test tube. When the solu- 
tion has boiled sufficiently, the delivery tube is disconnected, 
and the contents of the test tube transferred to a casserole. 
A drop of starch solution is added and sufficient dilute hydro- 

N 
chloric acid to dissolve the cadmium sulphide ; — iodine solu- 

^ 10 

tion is then run in from a burette until a blue color appears. 
ICC. — iodine — .0036 calcium sulphide ( CaS ). 

Alkalies. — For the determination of the alkalies the method 
of J. Lawrence Smith is generally employed, as follows: 

One gram of the finely divided sample is intimately mixed 
with an equal weight of ammonium chloride. Eight grams 
of precipitated calcium carbonate are then thoroughl} incor- 
porated with the mixture ; the mass is transferred to a capa- 
cious platinum crucible with a tight fitting lid, and heated 
over a Bunsen flame. The heat is applied gently at first, until 
fumes of ammonium salts cease, after which the crucible is 
heated to a bright red for one hour. After cooling, the fusion 
is transferred to a platinum dish, covered with water and al- 
lowed to slake. When thoroughly slaked, the solution is 
filtered into another dish, and evai)orate(l to about 50 c. c. 
when 2 grams anunoniuni carbonate are added. As soon as 
the ebullition ceases, the clear li(|ui(l is filtered off into a weighed 
platinum dish, and evaporated. A crystal of anunonium car- 
bonate should be added during the evaporation; it a precipi- 
tate separates it nuist be filtered. When there is no further 
precipitation, the solution is acidulated with hydrochloric acid 



ir)8 PRACriCAL CliM/iNT TliSTING. 

and taken to dryness on the water balli. When ])erfectly dry, 
the cldorides are broken loose from the (hsh and earefully 
ij^niled at a (hill red heat to constant weij^ht. This f^ives the 
combined chlorides — NaCl + KCl. 

lu)r their se])aration, the mixed chlorides are taken u]) with 
a few c. c. of water and a drop or two of liN'drochloric acid, 
and heated on the water bath. There are fre(|nently a few 
grains of insoluble matter; this should be filtered off and 
ignited, and its \vei<^"ht deducted from that of the combined 
chlorides. To the solution of the chlorides, I to 2 c. c. of a 
solution of i)latinic chloride are added, after which it is evapo- 
rated on the water bath until crystallization l)e<.,nns. A few 
c. c. of water and an ecpial (piantity of alcohol are added ; the 
insoluble i)otassium ])latinic chloride is filtered off on a 
weii^hed (iooch crucible or tared hller, washed with alcohol un- 
til the washiufi^s are colorless, dried at ioo° C. for one hour, 
and weighed as potassium platinic chloride (Kj,PtClu). We 
then have : 

Wt. K.PtCl, X .194 = K.,0. 

WT. K.PtCl, X .307= KCl. 

Wt. NaCl X .531 :-=Na,0. 

Carbon Dioxide. — For the accurate determination of carbon 
dioxide in rocks or cements, a train, such as is represented in 
V\^. 104, is em])loyed. It consists of a washin^i^ bottle, contain- 
ing dilute sulphuric acid, followed by a tower of caustic potash 
connected to a tap funnel leading to the bottom of a 4-oz. Erlen- 
meyer flask. From this flask a tube leads to an upwardly in- 
clined condenser, followed in this order by a "U" tube of calcium 
chloride, a tube of anhydrous copper sulphate, a second tube of 
calcium chloride, and then the two weighed "U" tubes, filled 
with soda lime for the absorption of the carbon dioxide and pro- 
vided with stop-cocks. These are followed by a "U" tube con- 
taining soda lime in its inner and calcium chloride in its outer 
arm, which leads to a suction pumj) or aspirator bottle. Before 
using the apparatus a current of C()^ should be passed through 
the first three "C" tul)es, in order to saturate any free lime. It 
should be followed by a liter of ])urifie(l air. 

To operate the apparatus, a weighed portion of the sample, 
ranging from 0.5 gram of a limestone to 5 grams of Portland 
cement, is introduced into the iM-lenmever flask and covered 



CHEMICAL ANALYSIS. 



199 



with water. All the stop-cocks are opened and a liter of air 
is aspirated through the apparatus. The soda lime tubes are 
then removed (with stop-cocks closed) and placed in the bal- 
ance case for 15 minutes, after which they are weighed. The 
operation is repeated until both tubes reach a constant weight. 
Fifty c. c. of I — I hydrochloric acid are then introduced into 
the tap funnel, and, with the train connected up, allowed to 
run into the fiask. When the reaction becomes weak, air is 
slowly aspirated through, the solution in the flask gradually 
brought to boiling and allowed to boil for several minutes, 




Fig. 104 — Apparatus for Determining Carbon Dioxide. 



after which the ilamc is removed and a couple ol liters of air 
aspirated. The stop-cocks are then closed, the weigiied tul)es 
removed to the l)alance case, and, after standing 15 minutes, 
are weighed. They are then again connected with the train, 
and, after a liter of air is aspirated, weighed, and this is re- 
peated until a constant weight is attained. Tiie gain in weight 
is carl)on dioxide — CO,,. 

For more rapid w(^rk, some operators i^refer the small gas 
bottles, an excellent form of which is shown in Mg. T05. A 
weighed quantity of the sample is introduced into the lower 



200 



PRACTICAL CEMEXT TESTIXG. 



part of the bottle and covered with water. The inlet tube which 
leads to the bottom of the flask is filled with i — i hydrochloric 
acid, while the other is ^ filled with strong sulphuric acid to 
absorb any moisture that might escape during the operatioa 
When everything is prepared the bottle is wiped clean and 
weighed, after which the hydrochloric acid is admitted to the 
sample. \\'hen the first reaction is over, a light suction is ap- 
plied to the outlet and air is aspirated until the bottle reaches 
a constant weight. The loss from 
bon dioxide — CO.. 



the original weight is car- 





Carbon Dioxide and Water.— For the determination of both these 
constituents in a cement or rock, the Shimer crucible ( Fig.io6) is 
found very convenient, 
and its operation is de- 
scribed at some leng^th 
by Meade. ^ The newer 
form of crucible is a con- 
siderable improvement 
over the old type in that 
it is provided with a 
circulating" chamber for 
water. The crucible is 
Fig. io5.-Apparatus ^et up in a train having 

for Determining on One side an aspirator. 

Carbon Dioxide by a calcium chloride and 

Loss of \\ eight. ^ ^^^3^-^ p^^^^j^ j^j. ^Q 

purify the air entering the apparatus, and on the other side a 
weighed calcium chloride tube followed by a weighed potash 
bulb and guard tube filled with calcium chloride. 

The weighed sample is placed in the crucible, and the cap is 
made air tight by means of a rubber band between it and the 
crucible. A circulation of water keeps this band from becom- 
ing hot. With a slow current of air passing through the ap- 
paratus, the crucible is heated by a strong Bunsen burner for 
ID minutes, followed by a blast for 20 minutes longer. The 
lamp is then removed, after which the aspiration is continued 
for about 10 minutes. Tlie tubes are then disconnected and 
weighed, observing the same precautions as in the preceding 
methods. 



Fig. 106. — The Shimer 
Crucible. 



'i:.xamination of Portland Cement," by R. K. Meade. 



CHEMICAL ANALYSIS. 201 

RAPID METHODS FOR CONTROL WORK. 

In making complete analyses of the raw materials or the 
finished product, the methods customarily followed in the mills 
are practically a condensation or simplification of the preced- 
ing general method. Corrections are never applied, the silica 
is evaporated but once and generally baked for 15 or 20 min- 
utes; only one precipitation is made for lime and magnesia, 
the former of which is determined volumetrically, while both 
gravimetric and volumetric methods are employed for mag- 
nesia. The accuracy thus obtained is less than that of 
the general method, but the errors are usually systematic and 
hence are comparativel> unimportant in control work which 
requires the determination of variations, rather than absolute 
quantities. 

For the proportioning of the raw materials, the lime alone 
is customarily determined, it being assumed that the other in- 
gredients vary in more or less of a fixed ratio. Proportioning 
is occasionally fixed by the silica content, but the use of this 
method is infrequent, and much less accurate and satisfactory. 
For the rapid determination of lime, the following two methods* 
represent the best practice, the first method depending upon 
titration with potassium permanganate, and the second upon 
titration with standard acid and alkali solutions. 

''Method 1. — In American practice this method is used most 
commonly and seems to enjoy the greatest favor among ce- 
ment chemists. It requires a potassium pcrnianganatc solu- 
tion of such strength that i c. c. =- 0.005 gram calcium car- 
bonate or calcium oxide, depending on whether a raw mixture 
or burnt cement is to be analyzed. The method is carried out 
for limestone as follows : 

"Weigh out 0.5 gram of the finely ground sample into a plat- 
inum crucible and ignite over the lUuiscn burner 10 ilestr(\v 
all organic matter. Transfer the sample to a 300 c. c beaker, 
add 30 c. c. of water, cover with a watch glass, add \o c. c. of 
hydrochloric acid and a little nitric acid. I '.oil till all the si^luble 
matter is dissolved and all the carbon dioxide expelled. W ash 
off watch glass and dilute to about 150 e. c. with water pre- 
viously boiled. Add anuuonia slightly in excess and heat to 
boiling. If the insoluble residue is low and it is not desired 

♦From "The Manufacture of Pornaiul Ceiuoiit, " ''^ \ v iii.iniimi 1 



202 PRACTICAL C EM EXT TESTLXG. 

to weigh the insoluble matter it is not necessar} to filter it 
oft*. The calcium oxalate is precipitated in the boiling hot solu- 
tion as usual by the addition of 40 c. c. of a hot solution con- 
sisting of 20 c. c. of concentrated ammonium oxalate solution 
and 20 c. c. of water. Stir for several minutes and let settle for 
five minutes. 

"Decant the supernatant solution through an ashless filter, 
add 40 c. c. of hot water, decant, add another portion of hot 
water and decant for the third time. Xow transfer the pre- 
cipitate to the filter and wash three or four times with hot 
water. To determine whether or not the precipitate has been 
washed sufficiently, catch a few c. c. of the last filtrate on a 
watch glass, add a drop of sulphuric acid and one drop of potas- 
sium permanganate solution. If the liquid shows a strong red 
color the washing is finished, if the color is discharged further 
washing is necessary. The calcium oxalate is now washed back 
into the beaker in which it was precipitated, using hot water 
and diluted to about 200 c. c, if necessary. Place the beaker 
under the funnel and run through the filter into the beaker 
30 c. c. of dilute sulphuric acid (i ^■olume of acid to 3 of water). 
\\'ash the filter thoroughly with hot water and stir the con- 
tents of the beaker while running in the acid. Heat liquid 
to about 80^ degrees C, and titrate with the permanganate solu- 
tion to a famt pink color which should not disappear for two 
minutes. 

"The potassium permanganate solution should not be stand- 
ardized agamst iron or ammonium ferrous sulphate, but against 
calcite checked repeatedly by the gravimetric method of cal- 
cium determination. 

"R. K. ^leade'-' proposes to keep the iron and alumina in 
solution by the addition of 5 per cent, oxalic acid, the calcium 
being precipitated by ammonium oxalate and determined vol- 
umetrically with a standard permanganate solution. The re- 
sults have been found by ^leade to be very satisfactory. 

"Method 2. — The acid alkali methods, owing to their rapidity 
and simplicit}, are frequentl}- made use of, but great caution 
is necessary in their use, and the results should be carefully 
checked gravimetrically from time to time owing to the fact 
that these methods are subject to errors. Larger amounts of 

*"Cement and Engineering News,"' June, 1903. 



CHEMICAL ANALYSIS. 203 

alumina and iron influence the results most decidedlv. S. B. 
Newberry'^ proposes the following working method: 

"Prepare a n/5 solution of hydrochloric acid and a n/5 caus- 
tic soda solution, standardizing with pure Iceland spar, which 
has been analyzed gravimetrically. One-half gram of pure spar 
should exactly neutralize 50 c. c. of acid. 

''Weigh out ^ gram of a finely ground limestone, transfer to 
an Erlenmeyer flask of about 500 c. c. capacity provided with 
a rubber stopper and a thin glass tube 30 inches long, to serve 
as a condenser. Run into the flask 60 c. c. of the 1-5 normal 
acid, attach the condenser and boil gently, allowing no steam 
to escape from tube, for about two minutes. Wash down the 
tube into the flask with a little water. Remove the condenser 
and cool the solution thoroughly by immersing the flask in 
cold water. When quite cold add five to six drops of phenol- 
phthalein solution (i gram in 200 c. c. alcohol) and titrate back 
to first pink color with 1-5 normal caustic soda solution. It 
is important to recognize the point at which the first pink color 
appears throughout the solution, even though this may fade 
in a few seconds. If the alkali be added to a permanent and 
strong red color the lime will come too low. The amount of 
acid used is called the first acid and the alkali used to titrate 
back, the first alkali. 

''In case the materials contain a very small amount of magne- 
sia the operation ends here and the calculation is simply : Num- 
ber of c. c. acid minus number of c. c. alkali multinlied by 2 x 
0.56 = per cent, calcium oxide. In this case it is unnecessary 
to cool the solution, and a permanent red is obtained at the 
point of neutralization. 

"The determination of magnesia proceeds as follows : 

"Transfer the neutral solution to a large test tube 12 inches 
long and i inch inside diameter marked at 100 c. c. Meat to boil- 
ing and add 1-5 normal caustic soda solution, about one c. c. at a 
time, boiling for a moment after each addition until a i\QC\^ rod 
color is obtained which does not pale on boiling. 

"This point can be easily recognized within one-half c. c. after 
a little practice. Note the nunilicr of c. c. soda solution aildcd 
to the neutral solution as second alkali. Dilute to icx^ c. c, boil 
for a moment and set the tube aside to allow the i)recipitate to 

*"('('iiUMi( and I'jnKiiHHM-iiiK Nows," Murcli. r.>it;'.. 



204 



PRACTICAL CEMENT TESTING. 



settle. When settled take out 50 c. c. of the clear liquid by 
means of a pipette and titrate ])ack to colorless with 1-5 normal 
acid. Multiply by 2 the number of c. c. of acid required to neu- 
tralize and note as second acid. 

''Calculation : 

"Second alkali : second acid X2XO.40 = per cent, magnesia. 
First acid x (ist alkali + 2d alkali — second acid) x 2 x 0.56 = 
per cent, calcium oxide." 

SUPPLEMENTARY. 

The Detection of Adulterants. — The common adulterants of 
Portland cement are natural cement, limestone, cement rock^ 
slag, cinder, sand and in foreign cements, hydraulic lime. 
Some of these, moreover, so nearly approach the chemical com- 
position of cement that they may readily escape detection in 
ordinary analysis, so that recourse must be made to special 
methods in order to determine their character and amount. 

The chemical tests most generally employed for this purpose 
are : — loss on ignition, weight of carbon di-oxide absorbed, 
and reduction of potassium permanganate. 

The determination of loss on ignition has already been de- 
scribed,* and for a normal Portland cement should rarely ex- 
ceed 2^ per cent. If much above that figure and the cement is 
not underburned, as shown by the specific gravity, it would in- 
dicate the presence of natural cement, a carbonate rock, or hy- 
draulic lime. 

The amount of carbon di-oxide absorbed is obtained by plac- 
ing about 3 grams of finely ground material in a stream of the 
gas, then drying it over sulphuric acid and determining the in- 
crease in weight. Normal cement rarely absorbs over 0.05 per 
cent. ; excess indicates natural cement or hydraulic lime. 

The reduction of potassium permanganate test is made by 
treating one gram of finely ground cement with a mixture of 50 
c. c. of dilute sulphuric acid and 100 c. c. of water and then 
titrating with a potassium permanganate solution of known 
strength. A gram of normal Portland cement should not reduce 
more than 3 milligrams of permanganate, while a gram of slag 
reduces from 45 to 75 milligrams. 

The presence of cinder or sand may be detected readily by 

*See page 186. 



CHEMICAL ANALYSIS. 205 

treating the cement with dilute (i :i) hydrochloric acid, the sand 
or cinder remaining as an insoluble residue, which may be ex- 
amined to determine its character. The presence of slag also 
may generally be detected by the same treatment, due to the 
evolution of hydrogen sulphide gas which can be recognized by 
its characteristic odor or by placing over the vessel a filter paper 
moistened with lead acetate which will be turned black if this 
gas is present. 

The specific gravity of Portland cement is much greater than 
any of its adulterants and this gives another method of detec- 
tion. Portland cement averages a specific gravity of 3.15, nat- 
ural cement 2.85, slag 2.85, limestone 2.60, sand 2.65, and cinder 
2.70, so that a large- amount of adulteration could readily be 
observed in the ordinary specific gravity test. However, on ac- 
count of the many other conditions that also operate to produce 
a low specific gravity this test alone is never positive, but the 
difference in specific gravity between cement and its adulterants 
may be utilized in the following method devised originally by 
Le Chatelier : 

This method consists in preparing a liquid with a specific grav- 
ity of about 2.95 by diluting iodide of methylene (sp. gr. 3.34) 
with benzole or turpentine and adding the cement, which sinks 
in the liquid while the adulterant floats on the surface. The 
liquid is conveniently prepared by placing about 12 c. c. in a 
small test tube with a crystal of aragonite which has a specific 
gravity of 2.95 and then slowly adding benzole with constant 
stirring until the li(juid is neutral to the crystal so that it will 
neither sink nor float. It is then quickly transferred to the scp- 
aratory funnel (Fig. 107) which should be about four-fifths full. 
One to two grams of the sample to be tested are then weighed 
and brushed into the liquid, stirred a few moments witli the 
platinum rod, then tightly stoppered and set aside for aboui half 
an hour, while the se])aration takes place. Bv careful manipu- 
lation the two portions may be drawn off separately, caught on 
tared filters and after washing with benzole, dried ami weighed, 
thus giving the relative amount of the adulteration, which may 
then be subjected to analysis and its character determined. Care 
nuist l)e taken in 0])erating this apparatus to keei> it tightly 
closed or the specific gravity of the liquid will rai)idly increase 
due to the evaporation of the benzole. 



2o6 



PRACTICAL CEMENT TESTING. 



The microscope affords another means for the detection of 
adulteration. It is best to employ a low power objective^ about 
§ inch, and to examine that part of the cement which passes the 
No. 100 and is retained on the No. 200 sieve. The cement clinker 
can easily be recognized by its honeycombed appearance and 
its dark, almost black, color. Underburned clinker appears 
brownish and semi-transparent. Plaster of Paris appears soft 
and white. Slag is characterized by its grey color and angular 
fracture. Raw rock has al)out the same color as clinker, but 
lacks its honeycombed appearance. The debris of iron and 




Fig. 107. — Apparatus for Detecting Adulterations by Separa- 
tion with Methylene Iodide. 



flint from the mills as well as particles of unburned coal may be 
readily recognized. 

Equipment. — The following list gives the apparatus and chem- 
icals necessary in a practical routine laboratory running an 
average of say four samples a day. The articles marked with an 
asterisk (*) should be increased or diminished for greater or less 
volume of work, while those marked with a dagger (f) are only 
required in determinations of carbonic acid and the alkalies or 
in tests for adulterations. The cost of the list as given should 
be from 250 to 300 dollars. 

A small equipment adapted to the occasional testing of single 



CHEMICAL ANALYSIS. 



207 



samples for the common constituents will cost from 100 to 150 
dollars. 

APPARATUS. 



Chemical balance (sensible 

to 0.1 mg.). 
Rough balance (sensible to 
• ig.). 
*4 platinum crucibles, 
fi " Gooch crucible, 

fi " dish — TOO c. c. 

I 2^-inch agate mortar. 
I small steel mortar. 
*2 5-inch desiccators. 
*I2 4-inch casseroles. 
*I2 No. 3 beakers. 
*I2 No. 4 " 
*6 No. 6 
*6 No. 8 
*I2 4-inch watch glasses. 
*I2 6-inch " " 

*I2 2-inch funnels. 
*I2 3^-inch funnels. 
3 50 c. c. burettes. 
I TOO c. c. burette. 

1 1,000 c. c. graduated cylinder. 

2 100 c. c. graduated cylinders. 

3 pipettes (to c. c. — 25 c. c. 

— 50 c. c). 
1,000 c. c. volumetric flasks. 
I litre flasks. 
500 c. c. flasks. 
500 c. c. filter flask. 
12 oz. Erlenmeyer flasks. 
8 oz. 
washing bottle. 



2 
2 
2 

I 
2 

t2 
tl 

ti CaCl,, jar. 

fi 12-inch condenser. 

t4 8-inch U tubes. 



U 

ti 
ti 



6-inch U tubes (with ground 

glass stojjpers). 
2-oz. separatory funnel. 
CO^ bottle, 
aspirator bottle or suction 

pump, 
special separatory funnel 

(for adulterations). 
doz. specimen bottles, 
doz. 6-inch test tubes, 
doz. No. o porcelain crucibles, 
doz. rubber tips. 
200^^ C. thermometer, 
water still, 
water bath, 
hot plate (11 X 18). 
drying oven. 
Bunsen burners, 
blast lamp and bellows, 
retort stands, 
clamps. 

burette stands, 
filter stands (double), 
test tube rack, 
clay triangles. 

pair crucible tongs (nickel), 
cork borer. 

Glass rods and tubing. 
Wire gauze. 
Asbestos board. 
Rubber tubing. 

" stoppers. 
Corks 
Files. 

small camel's hair brushes. 
6-inch spatulas. 



CHEMICALS. 



Hydrochloric acid. 

Sulphuric acid. 

Ammonia. 

Nitric acid. 

Oxalic acid. 

Hydrofluoric acid. 

Sodium carbonate. 
tAmmonium chloride, 
t " carbonate, 

t " oxalate, 

Microcosmic salt. 

Barium chloride. 

Zinc. 

Potassium permanganate. 
fSoda lime. 

Calciimi chloride. 
tPotassium hydrate. 
" nitrate. 

" bisulphate. 



Sodium hydrate. 
tCoppcr sulphate. 
fPlatinic chloride. 

Silver nitrate. 

Lead acetate. 
fCalcium carbonate. 

Alcohol. 

Iron wire. 

Phcnol-phtlialein. 
tMethvlono iodide. 
flkMizole. 

Limestone, 

Iron sulphide. 

Qualilativi- filter paper. cm. 

Ashless qualitative filter 
paper. otn, and IT cm 

Ashless (itialitativo filter 
paper f<»r sulphate. 7 cm. 



20S 



PRACTICAL CEMEXT TESTING. 



It would scarcely be profitable to give descriptions of the vari- 
ous fixtures, hoods, sinks, water and gas arrangements, etc., 
necessar\- to equip a chemical laborator}-. since each particular 
laboratory has different conditions to meet, and each chemist 
has indi\'idual preferences as to their arrangement. A conven- 
ient bath for running down solutions and evaporating silicas 
can be made by placing a steam coil in the bottom of a hood 
and covering it with 2 or 3 inches of sand. An automatic motor 
driven blast will also be found a great convenience and time- 
saver. The author has installed in the Philadelphia Laboratories 
a sysiem of ovens and plates heated by electricity which have 



T-\3LE XLVL- 



Aluminum . 
Arsenic ... 
Barium ... 
Bromine. . 
Cadmium. 
Calcium . . 
Carbon. . . . 
Chlonne . . , 
ChromiomL. 
Hydrc^en . 

Iodine 

Iron 

Lead 



■Sjnabols and Atomic Weights of the Elements Entering 

into the Analysis of Cement. 
(Atomic Weights Based on H = i.ooo.) 

Al 26.9 Msfnesium Mg 

As 74.4 Manganese. Mn 

Ba 136.4. Nitrogen N 

Br 70.36 Oxygen O 

Cd III. 6 Phosphorous .. . P 

Ca 30.S Platinum P: 

C 1 1. 91 Potassium K 

CI 35-i8 Sihcon Si 

Cr 51.7 Silver Ag 

H 1. 00 Sodium Na 

I 12;. 9 Sulphur S 

Fe 55.5 Tin 5n 

Pb -205.35 Zinc Zn 



24.18 
54-6 

13- 93 
15.88 

30.77 

193-3 
3S.86 

2S.2 
107.12 

22.88 

31.83 

iiS.i 
64 9 



given great satisfaction and are recommended where an elec- 
tric current is convenient and cheap. 

Valne of Chemical Analysis. — Only the mills and the large 
private and permanent laboratories have need of a chemical 
laboratorv- for the resting of cement. In the miUs, the control 
of the product rests entirely on the composition of the raw ma- 
terials and there a laboratory- is a positive necessity. From the 
consumer's standpoint it is only necessary- to know that the in- 
jurious constituents, principally magnesia and sulphuric acid, are 
\\-ithin allowable limits. With the magnesia little trouble is ever 
encountered since none of the domestic cements average over 
3 ^^ 3J P^r cent., which is entirely safe for all ordinary construc- 
tion. The content of sulphuric acid should be checked from time 



CHEMICAL ANALYSIS. 



209 



v> 




B 




X3 












Im 




d 




bfi 









(-1 




u 


hH 


ni 


.> 


J3 


U 


H 


X 


n 


a; 




Xi 


'^ 


i^ 



o 





MOO O^O^^o>-< " O r^a\CN0O0O r^fS ro 

■^ M 0^ ■* ii-)0 rooc r^ CT>. On On t^SO -^ 
t-H 00 rOLOrJ-t^MMD M 0) l^LO 1^00 00 O M 
VO Mr^N 0\0 wOO'Ot^ rOVO u-iGO ^ M 00 t^ 

0\ OnO OiC) OnOnOnO ONO\ONO\CfNO\Cf\ 




OloOVO ONN NVCt^N w Td-ri-u-iw w QOO 
N -^00 Onm N LOU-iT^OOO M r^t^'^N 

i-hVOOO ONM 0^0 ^<^0^.•^vO loO ON'OrO 
tJ- c^ 10 t^OO M LOVO rj-u-)j Tj-rr>t-»mi-iO "^ 


c5 M d w d M HH d G d cs d d d d d d d 


c 

m 


0^ 

c ; ^.0^0 cTc/^-'o" o"o 

u 


1 


t- t- to 50 

'^ '^ '^ " " ~ «,^ ^^ "^ n n — . 
000 «o c/f c/^V^ R - - n^ 


a 

3 


Tf t^ t^ t^ fO lOVO '^J- t^ >-i 1^ fDOO VO 00 
t^ r^vO ^00"ONTl-«i-rl-i-iO u^^O Li-i ON CN 
U-) r^ t^ u-^ ro OnOO ^ rl- >-i "->^ 00 rO lO N NO 
VONO roroN OnO 0\ri-r^ unoo 00 -^ ro ro --^ lo 

d\o\O\<^6\d^<i\C!\o\o\0 d d cno d cKd 


1 


ro^^t^M Ovr^o^"-! N -^r^ONO Olo 
00 rorD'^N LoOvN 'too (NJOVONO M rot^ 

d d d d d d d- d d >-< cNi ro d -^ i-< N 


1 

eg 


00 
0*5 jSm^m 606^00^ ..p 

C/) ^COO^ol,, ajC/3^^^ -rt^^-'O^ 
rtO C/)«Ur?U rtojrtOu"'^^,'^ 
UC/) ffi ^ UuUC/)UC/5 U 

u u u 


1 
% 


6666666m c/dodoOOOOOO „ 
mmimmmmm _ ^^uuuUq 



210 



PRACTICAL CEMEXT TES'I IXG. 



to time and not allowed to exceed 1.75 or at most 2 per cent., but 
the best method for the consumer, unless he has a permanent 
laboratory, is to send occasional samples to one of the many 
private laboratories for an analysis of sulphuric acid and occa- 
sionally for magnesia, which will cost but 2 or 3 dollars a sam- 
ple, and thus will effect a great saving over the cost of making 



TABLE XLVIIL— For Reducing Values of Ba SO^ to SO3— 
Based on the Factor 0.343. 





0.00 


0.01 


0.02 


0.03 0.04 


0.00 

0. 10 

0.20 

0.30 

0. 40 

0.50 

0.60 

0. 70 

0.80 

0.90 

I 00 


0.0000 
0.0343 

0.06S6 
0. 1029 

0.1372 
O.I7I5 
0.2058 
0.2401 

0.2744 
0.3087 

0.3430 


0.0034 
0.0377 

0.0720 
0. 1063 
0. 1 406 

0.1749 

0. 2092 

0.2435 
0.2778 
0.3I2I 
0.3464 


0.0069 
0.0412 
0.0755 
0. 1098 
O.1441 
0.1784 
0.2127 
0.2470 
0.2813 
0.3156 
03499 


0.0103 
0.0446 
0.0789 
0. 1 132 

0.1475 
O.1818 
O.2161 
0.2504 
0.2847 
0.3190 

0.3533 


0.0137 

0.0480 
0.0823 
O.I 166 
0.1509 
0.1852 
0.2195 
0.2538 
0.2881 
0.3224 
0.3567 




0.05 


0.06 0.07 


o.os 


0.09 


0.00 

10 

0.20 

030 

040 

0.50 

60 

0. 70 

080 

0.90 

1.00 


O.OT71 
0.0514 
0.0857 
0.1200 

0.1543 
0.1886 
0.2229 
02572 
0.2915 
0.3258 
0.3601 


0.0206 02iO 
0.0549 0.0583 
0.0892 0.0926 
0.1235 0.1269 
0.1578 O.1612 
0. I921 0.1955 
0.2264 0.2298 
0.2607 0.2641 
0.2950 0.2984 
0-3293 0.3327 
0.3636 0.3670 


0.0274 
0.0617 
0.0960 

0.1303 

0.1646 
0.1989 

0.2332 

0.2675 
0.3018 
0.3361 
0.3704 


0.0309 
0.0652 
0.0995 
01338 
O.1681 
0.2024 
0.2367 
0.2710 
03053 
0.3390 
0.3739 



these tests himself. A few simple reagents and test-tubes will 
be sufficient for making the adulteration tests just described, 
but that need be the only outfit required. The complete analy- 
ses made by the permanent laboratories are more a matter of 
record and experiment, than of value in the acceptance of ma- 
terial. 



CHEMICAL ANALYSIS. 



211 



TABLE XLIX.— For Converting Mg P^ O- to Mg O- 
Based on the Factor 0.^62. 





0.00 


0.01 


0.02 


0.03 


004 


0.00 

0. 10 

0. 20 

30 

0. 40 

0.50 

60 

0. 70 

0.80 

0. 90 

1.00 


0.0000 
0.0362 

0.0724 
0. 1086 

0. 1448 
0. I8I0 
0.2172 

0.2534 
0.2896 

0.3258 

0.3620 


0.0036 
0398 
0.0760 

O.II22 

1484 
0.1846 
0.2208 
2570 
0.2932 
0.3294 
0.3656 


0.0072 

0.0434 
0.0796 
O.II58 
0. 1520 
0.1882 
0.2244 
2606 
0.2968 
03330 
0.3692 


0.0109 
0.0471 
0.0832 
O.I 195 

0.1557 

0. I9I9 
0.2281 
0.2643 

03005 

0.3367 
0.3729 


0.0145 
0.0507 
0.0868 
O.1231 
1593 
1955 
0.2317 
0.2679 
03041 
0.3403 
0.3765 




0.05 


0.06 


0.07 


0.08 


0.09 


00 

0. 10 

0. 20 

0.30 

0.40 

0.50 

60 

70 

080 

90 

1. 00 


0.0181 
0.0543 
0.0905 
0.1267 
0.1629 
0. 1991 

0.2353 
0.2715 
0.3077 

0.3439 
0.3801 


0.0217 
0.0579 
0.0941 
0. 1303 
1665 
0.2027 
0.2389 
2751 
0.3113 
0.3475 
0.3837 


0.0253 
0615 
0.0977 

0.1339 
0. 1701 
0.2063 
0.2425 
0.2787 
03149 
03511 
0.3873 


0.0290 
0.0652 
0. 1014 
0.1376 
1738 
0.2100 
0.2462 
0.2824 
0.3186 
0.3548 
0.3910 


0.0326 
0.0688 
0. 1050 
1412 
1774 
0.2136 
0.2498 
0.2863 
0.3222 

03584 
3046 



CHAPTER XII. 

SPECIAL TESTS. 

The tests considered in this chapter are employed but rarely 
in ordinary routine, and have Httle, if any, importance, so far as 
the customary reception tests are concerned. Only sufficient 
will therefore be given to enable the operator to understand the 
reason^ for their occasional employment and the common 
methods of making the determinations. 

Compression Tests. — These tests usually are made for the com- 
parison of dififerent sands and stones intended for use in con- 
crete, and for other purposes in which the concrete itself must 
be tested, and not the cement or mortar composing it. The test 
is frequently made for experimental purposes on cements or 
mortars, but rarely for purposes of reception. 

For tests of concrete, compression tests are the most suit- 
able for the reason that either tensile or transverse specimens 
must be of such a size, if reliable results are desired, that they 
are very unwieldy and awkward to handle. A 6-inch cube, 
however, is sufficient for tests in compression. 

The common form of specimen is that of a cube, 2 ins. on a 
side for mortars, and 6 ins. for concrete. The material fails gen- 
erally by pushing out the sides laterally leaving pyramidal pieces 
in the middle, the failure being in the nature of a shear along 
surfaces inclined about 30" to 35" with the vertical. Since the 
material fails at this angle, a cube evidently will not give theoret- 
ically true results, but its employment is so universal that it 
would be difficult to institute a change. Cylinders are often 
employed instead of cubes, because they can be filled more uni- 
formly, it being very difficult to thoroughly compact the cor- 
ners of the cube. The broken halves-of briquettes are also tested 
occasionally, but because of their small depth in comparison with 
the area they give abnormally great results. Johnson* states 
that half-briquettes should be multiplied by the correction factor 
0.83 to make the results obtained from them and from cubes 

*"The Material?) of Construction," by J. B. Johnson. 



SPECIAL TESTS. 



213 



comparable. For certain tests the author has used small c} 1- 
inders i in. in area and i in. high with very satisfactory results. 
The bearing surfaces of the specimens must be carefully 
dressed to true planes before test, and it is advisable to have one 
surface bearing on a ball and socket joint to correct for any 
slight angle between the planes of the surfaces. To take up 
small irregularities, it is common to rest the block on blotting 
paper, sheet lead, or plaster of Paris. When plaster is employed 
it is gauged, put between sized paper at both top and bottom of 
the specimen, on w^hich a very low stress is placed, the plaster 
setting while the cube is in position. The author uses three 
thicknesses of blotting paper at the top and bottom of each cube, 




4 

1 


J 



Fig. 108 —Mould for 6-in. Concrete 
Cubes. 



Fig. 109. — Mould for 6-in, 
Cylinders of Concrete. 



and finds this surface most satisfactory for rajnd and accurate 
work. The results obtained, when any of these cushions are 
used, will, however, be slightly lower than those from cubes 
having a direct bearing on the steel plates. l'\)r dressing llie 
surfaces a machine like that shown in l^g. 1 17. page J-o, may he 
used to advantage. 

h^or 6-in. cubes of concrete, a good form c^f mould made oi cast 
iron, is shown in Fig. 108. l-igures log and no give forms of 
cylindrical moulds, the latter being an inexpensive form made of 
sheet iron held by a cla.np. The J-in. cube numlds are made 
cither singly or in gangs (I'^ig. i 1 0- 

The machines usually enii)loyeil for tests oi conerele are the 



14 



PRACTICAL CEMEXT TESTEXG. 



so-called "universal" machines which can be made adaptable 
for tests of tension and cross-breaking, although entirely too 
cumbersome for making either of these tests on small briquettes 
or prisms of cement. A type of these machines is shown in Fig. 

1 12 ; power is necessary to op- 
erate them satisfactorily. For 
breaking- 6 in. cubes of the 
richer mixtures of concrete, a 
capacity of 150,000 pounds 
is necessary, and even this 
amount is occasionallyexceed- 
ed,although most concrete will 
fail under 100,000 pounds. For 
6-in. cylinders, 100,000 pounds 
will usuallv be sufficient. 




Fig. iio. — .\ Simple Form of Cylindri- 
cal Mould for Concrete. 



For tests of 2-in. cubes a similar "universal" machine of 
smaller capacity may be employed, or a special machine such as 
is illustrated in Fig. 113. In this, the load is due to hydrauHc 
pressure applied by the hand-wheel at the side, while its amount 
is read on the gauge. This particular machine is of 30,000 pounds 
capacity. Hydraulic machines, however, are generally less ac- 
curate and satisfactory than those in which the load is supplied 
through direct gearing. The compression attachment furnished 
with the long-lever cement machines is convenient for testing 
one-inch cubes and cylinders of mortar. A 150,000 pound uni- 
versal machine, and a long-lever cement machine w-ith attach- 
ments for compression and transverse tests will be sufficient to 
make all strength tests of cements, mortars and concretes. 



I 






Strength in Compression. 
—The ratio of compressive 
rtrengch determined from 
cubes or cylinders to tensile 
strength as determined from 
the standard briquettes wall 
vary all the way from 3 to 15, depending on the character of the 
specimens, their age, condition, richness, and method of treat- 
ment. The average ratio varies from 5 to 10. Johnson* gives 

*-'The >Iaterial9 of Construction," by J. B. Johneon. 



Fig. III. — Gang Mould for 2-in. Cubes. 



SPECIAL TESTS. 



215 



the following formula for this ratio based upon tests by Tet- 

majer on 1:3 mortar: 

compressive strength ^ . _ . ^ 

Ratio of- -^ — q -^ — =8.64 + 1.8 log A 

tensile strength ^ 

where A = the age in months. This gives a ratio of 8.6 for one 




Fig. 112 — The Olsen Universal Testing Machine. 

month, to 10.6 for i year, which is high for this mixture. The 
ratio generally increases both with age and with the richness of 



TABLE L.- 


-Showing the Relation of the Strengths of Cement U 


nder Different 








F 


orms of Stress. 




(From ''Cements, 


Mortars and Concretes," by M. S. F 


ilk.) 






' — Tension — ^ 


^Compression-N , — Bendins -- 


Shear . 






Ult. Resistance 


Ult. Kesistanco Extn^iiio Fihre 


IMt. Resistance 


inW^eks Mixture 


Pounds per 
Square Inch 


Pounds i)tir Stress in Ijlts. 
SquJire Inch per Sq. Inch 


Pouncis i)cr 
Squurt> Inch 






Air ' 


Water 


Air " Water Air Water 


Air Water 


( 







2-, I 


224 


i860 I()IO 695 625 


276 271 


1 ■ 




3 


106 


05 


f)2C) 880 273 247 


109 110 


( 




5 


68 


64 


543 537 168 158 


81 77 


4 -J 







266 


204 


24()0 24()o 860 887 


3't) 34t> 




3 


148 


i()() 


ii^(X) 1(140 302 381 


182 181 


( 




s 


I K) 


•"3 


()62 077 284 276 


i3<^ '3« 


104. to 113 







257 


2()2 


3400 46S0 loio 1350 


3S8 415 




3 


244 


272 


20S0 3340 748 973 


204 375 


( 




5 


177 


232 


1510 2960 545 810 


248 364 






Note.— Each value average of 9 tests. 





2l6 



PRACTICAL CEMEXTTESTIXG. 



the mortcir. Table L. gives a compilation by Falk"^ of the results 
of tests made bv Bauschinger. and sho\ys the relation between 
the strengths under different forms of stress ; each value rep- 

resents 9 tests. The ratio in 

this table varies from 13.2 to 
8.0, for specimens kept in air, 
and from 16.0 to 7.3 for those 
in water. These values are on 
the whole typical, although 
the maximum is abnormal. 

Transverse Tests. — It has 
frequently been urged that 
transverse instead of tensile 
tests be adopted for ordinary 
routine, on account of the sim- 
pler machines required, and 
the doing away with the ten- 
sile clip which is far from ac- 
curate. The great objections 
to them, however, are the lar- 
ger size of the -specimen, the 
fact that the least imperfection 
or chip near the center makes 
them almost worthless, and 
that greater uniformity or ho- 
mogeneity is required. For 
experimental purposes and for obtaining approximate data on 
strength, however, they are often employed. 

The size of specimen most frequently tested is a prism one 
inch square and either six or twelve inches ^^% 

long ; specimens two inches square are less 
often made. The standard of the French Com- 
mission is two centimeters square and 12 cen- 
timeters long. 

A common form of mould is shown in Fig. 
114, which may be improved by the use of end 
clamps instead of the cumbersome arrangement Fig. 114. — Mould 

given. Two forms of gang moulds for transverse {°^ Prisms o 
^ . .,, , 1 Mortar for Trans- 

prisms are illustrated on pages 231 and 232. verse Test. 




-Hydraulic Machine for Com- 
pression Tests. 




♦"•Cements, Moriars and Concretes," by M. S. Falk. 



SPECIAL TESTS. 217 

For testing ihese prisms, the attachments furnished with the 
long lever cement testing machines will be found most conven- 
ient. For rough tests three knife edges and a pail to hold sand 
or water are sufficient.* The knife edges should be rounded 
rather than sharp to prevent local crushing, and the prisms 
should be broken on their sides, so that the variation of the 
upper surface is minimized. 

The results of transverse tests are customarily expressed by 
means of the "modulus of rupture," which theore:ically is the 
tensile stress on the extreme fibre of the specimen, provided 
the material has not been stressed beyond its elastic limit. When 
extended to the point of rupture, the formula no longer holds, 
so that its use in the expression of ultimate values is purely 
empiric, and for this reason the ratio between tensile and trans- 
verse strength is not constant, but varies wi:h certain conditions. 

The modulus of rupture is written ^I = -^ -, in which w 

2 b h- 

= the center load, 1 = the span, b = the width and h ^ the 
depth of the specimen. To simplify calculations prisms one 
inch square are often tested on a span of 6| ins., in which case 
the center load equals one-tenth of the modulus of rupture ; two- 
inch prisms on a 5.^-inch span have the center load and modulus 
equal. 

The ratio between transverse and tensile strength varies from 
about 1.3 to 2.5. Generally, it varies inversely with the span, 
and directly with the cross-section, age and richness of the 
mortar. Durand-Claye, testing neat Portland cement on the 
standard specimen of the French Commission, found the ratio 
to be 1.92 at 7 days and 1.86 at 28 days. The ratios given in 
Table L. vary from 2.25 to 4.65 and increase with age : these 
values are exceptionally high. A series of tests by the author on 
specimensof 1 13 mortar are given on page 27^^. The accuracy of 
care'ully made tensile and transverse tests is about ct|ual. 

Tests of Adhesion. — That a cement or mortar should be capa- 
ble of a;Ib.c'rini; to an inert material is as important for purposes 
of construction as its cohesive properties, and yet this test is 
made only infrequently and then more for e.xperiniental research 
than for practical purposes. The tests are commonlv made to 
determine the adhesive strength oi cement pastes and mortars 

•For dewrlpUon of rough transver^H? testing luaobinerf, . v« page -XL 



2l8 



PRACTICAL CEMENT TESTING. 



to stone, metal, or to hardened mortar. The form of mould as 
recommended by the French Commission on Standard Methods 
of Testing is shown in Fig. 115. For the test, an adhesion block 
of a fine cement mixed with two parts 
of sand is first made in a special mould 
in the form of a half briquette, when 
hardened the adhesion surface is polished 
w4th emery paper, then fastened into the 
mould and the other half filled with the 
cement to be tested, Adhesion blocks of 
stone and metal are also employed. 

These tests may be made in an or- 
dinary mould filling half with a rich 
standard mortar and when hardened 
filling the other half with the mortar 
to be tested. A small block of iron 
in the center will give a smooth 
surface to the first mortar. Tests of 
adhesion to metal or stone may be simply made by preparing 
small pieces i x i x ^ in. of the adhesion surface material and 
placing them in the center of the briquette mould filling it on 




Fig. irf. — Form of Adhe- 
sion Mould and Block 
Recommended by the 
French Commission. 
Reproduced from Spald- 
ing's Hydraulic Cement 





Fig. 116. — Illustrating the Method for Conducting Shearing Tests, 




both sides with the mortar to be tested. When many of these 
tests are to be made, it is convenient to cut grooves in the sides 
of the mould and make the plates slightly over an inch in width 
thus holding the plate firmly and accurately in the center. 
Adhesive strength, like cohesive, is subject to the same varia- 



SPECIAL TESTS. 2ig 

tions due to consistency and richness of the mortar, age, envi- 
ronment, method of treatment, etc. The strength also increases 
with the roughness and porosity of the surface to which it is 
tested. The retempering of mortar is said to afifect the adhesive 
far more than the cohesive strength ; Chandlot states that this 
reduction may amount to 50%. 

The adhesion of cement mortar (1:2) to sandstone at 28 days 
averages about 100 pounds, to ground glass about 50 pounds, 
to iron from 50 to 75 pounds. 

Shearing^ Tests. — Although mortars and concretes are fre- 
quently subjected to shearing stresses, tests for shearing strength 
are but seldom made. The simplest method of making these 
tests is shown by the diagram in Fig. 116. The upper bearing 
should be slightly arched to avoid the introduction of other 
stresses and the load applied exactly in the center. A convenient 
specimen to test is a prism 1x1x6 ins., the distance between 
the upper bearings being 3 ins. and between the lower about 
3 1-16 ins., so that the upper bearing comes slightly within the 
lower. The total load is then twice the shearing strength in 
pounds per square inch. Tests are sometimes made by cement- 
ing three bricks together, the middle one projecting above the 
other two, and applying the load on the middle brick, but this 
method is liable to be inaccurate on account of the introduction 
of both adhesive and transverse stresses. 

From Table L., the ratio of shearing to tensile strength is seen 
to vary between 1.03 and 1.57. Mesnager gives the ratio as 1.2 
to 1.3. Tests by the author seemed to show a ratio but slightly 
over unity, but it may generally be considered safe to allow a 
shearing value of 1.2 times the tensile strength. On account of 
the frequent designing of structures to withstand shearing 
stresses, more data on this subject are nuich to be desired. 

Abrasion Tests. — These are made by forming a block of mor- 
tar or concrete and placing it in contact with a grinding surface 
under a definite pressure. A machine made by Riehle Rros. for 
this purpose is show^n in Fig. 117. It consists of a revolving cast 
iron disc, on which the specimen rests, while the pressure on it 
can be regulated by means of movable weights on the long 
lever. Sand and water are automatically fed between the speci- 
men and the (hsc. The test consists of determining the amount 
of wear i)r()(luce(l after the si)ecinu'n has been subject eil to a 



220 



PRACTICAL CEMEXT TESTIXG. 



given number of revolutions of the disc, under a definite 
pressure. 

The test has a certain vahie for determining the relative abra- 
sive properties of cement mixtures intended for use in sidewalks, 
floors, and other similar purposes. Sand mortars give better 
abrasion tests than neat pastes. ]\Ir. E. C. Clarke'^' found tha: 
a mixture of i part Portland cement to 2 parts of sand gave the 
best resistance to abrasion. 

Porosity. — The porosity oi a mortar or concrete is the amount 
of void space in the hardened specimen, and is usually expressed 




Fig. 117.— Machine for Testing the Abrasive Qualities of 
Cement. 

as the percentage of voids to the total volume. The determina- 
tion consis:s, therefore, of the measurement of the cubical con- 
tents of the specimen and the actual volume of its ingredients. 
The measurement of the specimen is simple if it be of regular 
form ; if not, it is weighed in water and again in air after it is 
completely saturated, the difference between these two weights 
divided by the weight of a cubic foot of water giving the appar- 
ent volume. Grease is sometimes rubbed on the specimen to 
prevent it changing its saturation and hence its weight during 
the process of weighing. The actual volume of the ingredients 

♦Transactions, American Society of Civil Enginesr? Vol. XIV., p. 167. 



SPECIAL TESTS 



221 



Is obtained in the same manner by weighing the dried specimen 
in air, and after saturation in water. The test pieces are dried 
at a temperature of iio° Fahr., weighed, then immersed in 

water until completely saturated, 
weig-hed in water, and then ag-ain 
in air. Complete saturation is 
effected either by exhausting the 
air by placing the specimen in 
w^ater under a pump, or by boil- 
ing it, the former method being 
preferable. The porosity is then 

p y^ , where D = weight air 

dry, W = weight in water after 
saturation and P = weight in air 
when saturated. The standard 
size of specimen for this test 
is a 3-inch cube, while the 
standard test is made on mor- 
tar (1:3) at the age of 28 days. 
The porosity of normal test- 
ing mortar averages from 20 to 
35 per cent. This test is never 
employed for purposes of recep- 
tion. 
Permeability. — The permeability of a mortar 

is the rate with which water under a fixed head 

will pass through it under definite conditions. 

This must not be confused with the test of 

porosity, which is a determination of void 

space, while permeability determines the rate 

at which water passes through those voids. 

There is no fixed ratio between the two proi)er- 

ties. 

Figure 118 shows the api)aratus of Trof. Tot- 

majer in which the specimen is made in the form 

of a disc, mounted in rubber cushions ami sub- 
jected to a definite water pressure, the rate at 

which the water rises in the tube being a meas- 
ure of the permeabihly. 




Fig. 118. — Tetmajer's Apparatus for 
Testing Permeability. 




Fig. in) 
Apparatus 
for Testing 
rornieability. 
Heccimmemled 
by the I'rench 
Commission. 



222 PRACTICAL CEMES'T TESTISG 

Figure 119 illustrates the device recommended by the French 
Commission on Methods of Testing, which is merely a cube of 
mortar to which a circular glass tube is cemented with a paste 
of neat cement. A rubber hose is fastened to the tube and 
connected with a resersoir oi water a: a heigh: of 4 inches. 3 
feet 3 inches, or 2>Z i^^^ 'O-^- ^-O- ^^ ^^.O meters) above the 
specimen, according to its degree of permeability. The test 
consists in measuring the amount of water passing through in 
an hour. The standard specimen is a 2 or 3-in. cube of 1 13 
mortar, 28 days old. and which has been immersed in water for 
at least 48 hours prior to the test. It is also advisable to allow 
the block to remain immersed during the determination. 

A rough test to determine the comparative permeability- of 
concretes may be made in the same manner, by cementing a 
one-inch iron pipe to a cube or disc of the concrete. This test, 
like that of porosity, is only made for purposes of experiment, 
and never for reception. 

NOTE ; — For data on porosity and permeability, the reader is referred to: 
R. Feret "Sur la Compacite des Mortiers Hydranliques ' in 'Annales des 
Fonts et Chaussees " Vol. IV, 1892; L. von Tetmajer in *'Methoden und 
Resukaie der Priifung der Hydraulischen Bindemittel" (Zurich, 1893); 
E. Chandloi — ■ Ciments et Chaux Hydranliques " ; Report of the French Com- 
mission on Methods of Testing the Materials of Construction, VoL I, 1894. and 
Vol. IV, iSq5 ; S. E. Thompson, Proceedings Am. Soc. of Ci%-il Engineers, 
Aug. 1903, pp. 648-649. from which cut 119 ^vas taken : and F. W. Taylor and 
S. E. Thompson in " Concrete — Plain and Reinforced. 

Yield Test of Mortar. — This test is occasionally employed to 
determine :he econoni} of different mixtures and consistencies 
of pastes and mortars. The yield of a mortar is the volume 
occupied by a paste or mortar gauged to a given consistency 
and made from a unit weight of cement or a mixture of ce- 
ment and sand. The test is made by weighing 1,000 grams of 
cement or sand mixture, gauging it with a fixed percentage of 
water and introducing it into a graduated cvlinder. in such a 
manner as to avoid the presence of air. and observins: the vol- 
ume occupied. 

Another method of making rhis rest is to form the paste into 
a block and after greasing the surfaces, to obtain its volume by 
weighing in air and suspended in water, or by actual dis- 
placement. 



SPECIAL TESTS. 22^ 

TESTS OF SAND. 

The testing of sand for use in mortar is so closely allied to 
that of cement that a brief mention of the methods employed 
to determine the relative value of different sands may well be 
made. The common tests employed for this purpose are its 
fineness, its degree of purity, the character of the grain, the 
specific gravity, the percentage of voids, and strength tests in 
comparison with a standard sand. 

The fineness is tested by sifting through a series of sieves, 
such as the Nos. 10, 15, 20, 30, 40, 60, 74, 100, 150 and 200.* 
A mechanical shaker, such as is shown in Fig. 34, page y2, is 
convenient for this purpose. The results are usually expressed 
as the percentage by weight passing each sieve. The size of 
sand is frequently indicated by its uniformity coefficient, which 
is the ratio of the diameter of those particles which have 60% 
of the sand smaller than itself, to the diameter of those which 
have 10% smaller. f'Sand having a coefficient of over 4.5 is 
a good coarse sand for concrete work, and in comparing dif- 
ferent natural sands the one having the highest uniformity co- 
efficient may be considered the best." 

The purity may be ascertained first by chemical analysis and 
secondly by the determination of the presence of loam, clay, or 
similar extraneous materials by elutriation methods. Elutria- 
tion consists of placing a weighed quantity of sand in a beaker 
or similar vessel, adding water, stirring it vigorously, and de- 
canting off the material remaining in suspension after 15 sec- 
onds standing, repeating the process until the water pours off 
clear, then drying and weighing the residue. The effect of these 
impurities on the mortar depends both upon their own character 
and that of the sand, and also upon the richness of the mortar. 
The consensus of opinion seems to be, however, that generally 
organic loam is deleterious, while small percentages of cla\ or 
finely divided mineral matter are beneficial. 

The character of grain is examined under a large reading 
glass, or microscope of low power. A rounded grain will give 
a denser mortar than an angular one, because it may be com- 
pacted more easily and hence has a lower void space. Tliis is 
well shown by comparison between the two standard testing 

♦These sizes are ret-oniniendod by Mr. W. H. Kuller. 

tFrom "Concrete-Plain and Reinforced." by F. W. Taylor and S. K. Tbonip 
son. 



224 PRACTICE!. CEMENT TESTING. 

sands — Ottawa and crushed quartz. The clause that sand 
should be sharp is a feature of man\ specifications, based upon 
a misconception or misunderstanding of this principle. 

The specific gravity may readily be determined in the same 
manner as cement,* or less accurately in a tall graduated glass 
cylinder by first filling it half full of water then introducing a 
weighed quantity of sand, a few grains at a time to eliminate 
air bubbles, and noting the displacement ; the specific gravity 
being the w^eight of the sand divided by the computed weight 
of the displaced water. The sand should be dried at a tempera- 
ture of 212° Fahr., before making this test. Sand has an aver- 
age specific gravity of 2.65. 

The determination of voids is made by filling a measure with 
sand, and then weighing its contents. The sands tested should 
all be filled in the measure in an exactly similar manner either 
loose, shaken or compacted, since the void space is appreciably 
affected thereby. A tall 1,000 c. c. cylinder is a convenient 
measure, and can be filled to the upper mark very accurately. 
The weight of the sand in grams divided by 1,000, or the vol- 
ume in c. c, then gives the net weight of the sand per c. c, and 
this divided by its specific gravity (2.65) and multiplied by 100 
gives the percentage of voids. The determination is made 
sometimes by ascertaining the amount of water that can be in- 
troduced in a measure filled with sand, but this method is very 
inaccurate, both on account of the absorption of water by the 
sand, and on account of the great dilftculty of eliminating air 
bubbles. 

Strength tests are made by testing mortar briquettes in ten- 
sion in comparison with standard sand or another sand of 
known value. Although the ratio of tensile strength to that 
of compression, cross-breaking, shearing and adhesion, varies 
considerably with different sands, the tensile test is usually con- 
sidered sufTficient for purposes of comparison. It is advisable 
to make other tests, however, particularly in compression and 
cross-breaking, if the facilities permit. 

TESTS OF STONE. 

The tests applied to stone are practically similar to those 
made on sand. For determining the size, sieves of o.io, 0.15, 

*See page 58. 



SPECIAL TESTS. 225 

0.20, 0.30, 0.45, 0.67, i.oo, 1.50, 2.25, and 3.00 ins."*' may be used. 

The specific gravity may be obtained in a manner similar to 
that employed for sand, or by weighing pieces of the stone in 
air and then suspended in water, the weight in air divided by 
the loss of weight in water giving the specific gravity. 

Voids are determined best in a cubic foot measure in the 
same manner as sand. The percentage of voids is then the 
weight in pounds necessary to fill the measure, multiplied by 
100, divided by the product of 62.3, the weight of water per 
cubic foot, times the specific gravity of the stone. 

The comparative values of stone in compression are deter- 
mined botli by crushing small cubes or cylinders prepared from 
the stone itself, and by tests of concrete made with it. Tests in 
compression are the only ones generally employed. 

♦These sizes are recommended by Mr. W. B. Fuller. 



CHAPTER XIII. 

APPROXniATE TESTS. 

This chapter deals with tests made not strictly in accordance 
with orthodox methods, but by means oi which it is possible 
to obtain information as to the quality of cement with little or 
no apparatus and without much experience in testing. Such 
tests are useful to the expert when examining material in a 
locality far removed from laboratories and apparatus, but are 
of especial value to the engineer of the small town, who uses 
but little cement, but wishes to know that what he does per- 
mit to enter his work is of the best quality. To send samples 
of the material to a distant laboratorv frequently causes un- 
necessary delays, is somewhat expensive, and is more or less 
unsatisfactory, for the reason that the samples in transit may- 
be subjected to conditions which will appreciably alter their 
physical properties, and also because the method of testing 
cannot then be supervised and, unless an elaborate report be 
submitted, it is difficult to know in what light to interpret the 
results. Generally speaking it is possible to obtain a very fair 
idea as to the quality of the cement by the use of the following 
tests, but on account of the inferior degree of accuracy they 
should always be interpreted rather liberally, or the material 
given the benefit of the doubt. Material positively unfit for 
serv'ice may, however, always be discovered bv their use. 

These approximate tests cover those of fineness, time of 
setting, strength, soundness and purity. Two tests that can- 
not be employed are quantitative chemical analysis and specific 
gravity, but for the small consumer the results of these tests 
are comparatively unimportant, and unless made with accuracy 
are apt to lead to misleading and erroneous conclusions. 

Fineness. — For determining the fineness of cement by a rough 
method, the employment of the X'o. loo sieve alone is recom- 
mended. It is true that there is no fixed relation between the 
results obtained on the X'o. lOO and Xo. 200 sieves, but never- 
theless the average ratio is fairly constant, so that for this test 
it can be assumed with a fair amount of accuracy that the 
residue left on the Xo. 100 sieve is about a third of that on the 



APPROXIMATE TESTS. 227 

No. 200. For ordinary testing, the finer sieve is the more im- 
portant, but, on the other hand, the greater part of the difficul- 
ties and irregularities of the determination lie in the obtaining 
and use of this sieve. Furthermore, it may be taken for granted 
that the manufacturers will not change the process of grind- 
ing because a comparatively small shipment is not to be tested 
on the finer sieve. 

For the test, therefore, a No. 100 sieve alone is to be procured ; 
neither a cover nor pan is necessary. It should be purchased 
from a reputable manufacturer who will guarantee the wire to 
be of proper diameter, while the average mesh per inch in both 
directions should be determined by actual count, and if not aver- 
aging between 96 and 100 the sieve should be returned. For 
this counting, a linen tester's microscope with a half-inch open- 
ing, such as is shown in Fig. 30, page 68, should be used. It may 
be purchased for 25 cents and will be found useful not only 
for this purpose, but also as a small pocket magnifying glass. 

For the weighing, a chemist's or druggist's balance is ad- 
vantageous, but an ordinary postal scale, weighing to 4 ounces, 
and showing a quarter-ounce clearly, may be employed. 

Best practice in specifications limits the residue retained on 
the No. 100 sieve to 8%, and that on the No. 200 to 25%. 
Assuming that the first residue is one-third of the other, if it 
is known that less than 8% or one-twelfth of the cement is re- 
tained on the No. 100 sieve, the cement may be taken as suffi- 
ciently fine. 

The test is made by weighing out 3 ounces of cement, plac- 
ing it in the sieve, and shaking it over a piece of wrapjMng paper 
until only a few grains pass through after half a minute's sift- 
ing. From 10 to 12 minutes will generally suffice. The speed 
of sifting may be accelerated by placing half a dozen small 
coins in the sieve, which can be removed from the residue 
with ease. After sifting is complete, the residue on the sieve 
is shaken out on a clean piece of paper and brushed on the 
pan of the scales. If weighing less than } of an ounce the ce- 
ment is satisfactory. The accuracy of the test may be increased 
hy weighing out 6 ounces originally, sifting about half at a 
time, and then weighing the combined residues which should 
not exceed half an ounce. 

FJutriation methods are occasionally emi)loved for rough 



•228 PRACTICAL CEMENT TESTLVG. 

tests of fineness, but except in the hands of the expert their 
resuts are apt to be very inaccurate, so that lor the average 
engineer their use is not advised. 

Setting. — For this test procure a pair of scales weighing a 
pound with comparative accuracy,"^ a druggist's graduate of a 
capacity of 8 fluid ounces, and an ordinary wash basin of china 
or paper, the former being preferable. Weigh out one pound 
of cement and measure 3^ ounces of water. Place the cement 
in the basin, form it into a crater, pour the water in the center 
and knead it vigorously for a minute and a half in accordance 
with the method given for making briquettes on page 120. At 
the end of this time the cement should be nearly of the normal 
consistency, as obtained by the ball method. f or of such con- 
sistency that a ball of the paste about 2 ins. in diameter formed 
by rolling in the hands, dropped from a height of two feet will 
not crack badly, nor flatten more than half.l If the consistency 
of the paste is too wet or too dry, repeat the process using 
more or less water until the proper degree of plasticity is ob- 
tained. If the test is made at a place where the scales and 
measure cannot be procured, this consistency may be experi- 
mentally obtained after a few trials. 

^^'hen a paste of proper plasticity has been made, form it 
rapidly into a rounded cake about the size of the cans in which 
shoe-blacking is usually furnished. One of these cans may 
actually be used to form the specimen if desired. The cake 
should be placed on a small piece of glass or metal, smoothed 
on the surface, and set aside in a cool place protected from, 
draughts of air and direct sunlight. 

Conservative specifications limit initial set to twenty min- 
utes, so at the expiration of that period, the time being taken 
from the moment the water is poured on the cement, the cake 
must be examined. If the surface appears and feels wet, and the 
cake can still be worked slightly without cracking, the require- 
ment is fulfilled. If, however, the surface appears dry and earthy, 
and an attempt to work cracks it, the material has failed. Ce- 
ment setting in less than 20 minutes usually heats up consid- 
erably, so if the specimen feels vv-arm during any portion of 
this period, it can be considered to fail in initial set. 

♦The postal scales used for the fineness test may be used by weighing out four 
ounces four times. 
■rSee page !>M. 
JA slight departure from this consistency is immaterial in this rough test. 



APPROXIMATE TESTS. 



229 



At the end of 10 hours, the cake should be re-examined and 
at that time should have become so thoroughly hardened th^t 
a firm pressure of the thumb nail, or a pencil point, will not 
make an appreciable indentation. If it is not hardened, but 
still soft, the material has failed in hard set, and in construction 
may set up so slowly that it will seriously interfere with the 
progress of the work. 

This rough examination will probably be more satisfactory 
and even more accurate, for a person unaccustomed to cement 
testing, than a test with such apparatus as the Gillmore needles 
which are easily mishandled, thus giving false results. 

Strength — By the Tensile Test. — It is believed that but two 
things should be done with the tensile test — do it right, or leave 
it alone. There is room for so many inaccuracies in the con- 
duct of this determination that when rough methods are em- 
ployed, the results are apt to be very far from true, but the 
fact that the tensile test has been made in spite of many dif- 
ficulties, tempts the operator to assign to them an undue 
amount of accuracy, Avhereas if other tests are made, known 
to be only approximate, they are seldom taken for more than 
they are worth. 

The test in tension, even by approximate methods, cannot 
be made in a manner differing essentially from that given in 
Chapter IX., although some of the appliances may be simpli- 
fied. Two things that should never be altered, however, are 
the moulds and the clips, for if any other form is emiilovctl. the 
values will be very different from those obtained under stand- 
ard methods. The mixing of the bri(|uettes may be performed 
in a wash basin, the appliances and method being simi- 
lar to that already given under "setting," excejU that the 
quantity should be two pounds for neat cement, ami for 
sand tests i| pounds of sand, thoroughly mixed with \ poun.l 
of cement. The amount of water for neat bric|iicties may 
gcnerall}- be taken at 0^ oimces, and 3 oimces for the sand mix- 
ture. 11ic sand may either be a local ov a standard sand, but 
if the local sand is to be used, several careful tests should be 
made to obtain the correclion taetor to reiluee the results to 
standard (|uanz, a few i)oiui(ls of which should be kept on iiand 
if possible. The mixing and moulding of the brii|ueltos is 
performed exaetl\- in tlu' manner described in ("hapter IX. 



230 



PRACTICAL CEMENT TESTING. 



For twenty-four hours after making, the briquettes must be 
kept in a clamp atmosphere. If no suitable box can be obtained 
for a make-shift closet, the briquettes must be covered with 
2L damp cloth, the points to be remembered being that the 
cloth must entirely cover even the sides of the moulds so that 
no dry air can penetrate under it, that the cloth must be kept 
wet by allowing the ends to rest in water, and that it must 
not touch the briquettes. A simple closet ma\ be made by 
utilizing an ordinary w^ash tub. Two or three inches of water 
are poured in ; a shelf made of two bricks and a short length 
of board ; and a cover made from a piece of old blanket held 
on by a few tacks, the ends hanging inside of the tub and 
touching the water. Any such appliance should be kept in a 
cool and, if possible, damp place, never exposed to sunlight or 
a current or air. 




Fig. I20 — Home-Made Cement Testing Machine. 

The briquettes may be stored in water in any suitable con- 
trivance, the same tub serving admirably. The briquettes 
should be placed on their sides, never flat; the water 
should be fairly pure, neither hot nor cold, and must be changed 
at least once a week. Pouring in extra water to replace that 
evaporated will not answer. 

For breaking the briquettes a spring balance testing ma- 
chine, similar to that shown in Fig. 74, is recommended. This 
machine costs from 60 to 80 dollars and is a good investment 
for any engineer using much cement, and if many tests are 
made will soon save its cost in the time and trouble wasted in 
operating any rough contrivance. If, however, but a few tests 
are to be made and the magnitude of the work will not war- 
rant such an expenditure, a device like that shown in Fig. 120 
may be employed. This particular machine was devised by 
F. W. Bruce, and was described in Engineering News,* by 
Lieut. W. M. Black, as follows: 

*Vol. XV., page 3&4. 



APPROXIMATE TESTS. 



231 



'The machine consists essentially of a counterpoised wooden 
lever 10 ft. long, working on a horizontal pin between two 
broad uprights 20 ins. from one end. Along the top of the 
long arm runs a grooved wheel carrying a weight. The dis- 
tances from the fulcrum in feet and inches are marked on the 
surface of the lever. A clip for tensile tests is suspended from 
the short arm, 18 ins. from the fulcrum. Pressure for shear- 
ing and compressive stresses is communicated through a loose 
upright, set under the long arm at any desired distance (gen- 
erally 6 or 12 ins.) from the fulcrum. The low^er clip for tensile 
strains is fastened to the bed-plate. On this plate the cube to 
be crushed rests between blocks of wood, and to it is fastened 
an upright with a square mortise at the proper height for 




> 



Fig. 121.— a Simple Mould for Making Prisms of Mortar. 

blocks to be sheared. The rail on which the wheel runs is a 
piece of light T-iron fastened on top of ihe lover. Tlie pin is 
iron, and the pin-holes are reinforced by iron washers. The 
clamps are wood, and are fastened by clevis joints ic^ the lever 
arm and bed-plate respectively. When great stresses are de- 
sired, extra weights are hung on the end of ihe long arm. 
Pressures of 3,000 pounds have been developed wuh it." 

Another more elaborate home-made eenuMit Irsling machuu' 
will be found described in hjiginec ring \\'\\>. \ ol. W .. page 
310. Such an apparatus, howi'vcr. will eost almost as nuich 
as one of the spring balance machines, i.s nuieh nioro ditVicnlt 
to oi)erale, and gives far less satisfactory results, (leiierally, 
therefore, it is advisable eilluM- t.^ nmenrr a small regular cc- 



22,2 



PRACTICAL C EM EXT TESTING. 



mcnt testing machine if the amount of testing will warrant it,, 
and if not to make tests of strength by cross-breaking, for 
which the apparatus is much simpler and more easily operated, 
and the results fully as accurate, if not more so, than those ob- 
tained in tensile tests with a crude device. 

Strength — By the Transverse Test. — This test is made on rec- 
tangular prisms — i x i x 6 ins., or i x i x 12 ins., preferably the 
latter. As all tests for strength are better criteria of the quality 
of the material when made of sand mortar than when of neat 
cement, the sand tests should be those generally made. As 
with tensile briquettes, it is preferable to make them of standard 
sand, but a local sand may be used if the correction factor is 




Fig. 122.— a More Elaborate Prism Mould. 

first obtained. Sand-mortar prisms have the advantage of 
being made with greater uniformity than those of neat cement, 
and may be tested with the simplest sort of device. 

The same general method for the making and storing of these 
prisms, already described for briquettes, is followed. A mould 
may be made of planed one-inch boards, and some inch wide 
strips of iron, or entirely of wood as shown in Fig. 121. A con- 
venient mould of cast-iron is shown in Fig. 122, w^hich will cost 
but 2 or 3 dollars, and will last for many tests. Any mould 
should be well oiled before use. 

For breaking the mortar prisms the simple arrangement 
shown in Fig. 123 is all that is necessary. The knife edges are 



APPROXIMA TE TES TS. 



23i 



made from a round piece of wood, one inch in diameter, and 
the load appHed by pouring sand into a bucket. For testing 
short prisms, heavier prisms or those of neat cement, a stronger 
arrangement for carrying the load must be provided, or some 
other device employed, but generally this easily made arrange- 
ment will be entirely sufficient. A more elaborate machine for 
transverse tests is described in Engineering News, Vol. XXX., 
page 469, the load being applied by pouring water into a pail, 
which operates through a long lever. A lever machine like that 
in Fig. 120, may also be made if desired. The author believes, 
however. In either purchasing a tensile machine or else in mak- 




FiG. 123. — Illustrating the Method of Making Transverse 
Tests Without Apparatus. 



ing rough transverse tests as described, for with the cheap ten- 
sile machines now in the market it is difficuh to imagine a case 
in which a piece of work was too small to warrant such a jnir- 
chase, but which would rc(|uire the employment of an elaborate 
but tedious and inaccurate home-made device, 
^rhe results of cross-breaking tests are expressed hv the for- 

nuila ^-r^Vo , ill which w -- the center load, 1 the si>an. b = 
2 b h- 

the width and h the depth of the specinu-n. l''or one-incli 
rectangles this becomes 3/2 w 1. The results of eri)ss-l)reaking 
tests expressed bv this f(^rnnil'\ \\:\\c betMi shown to give values 



234 PRACTICAL CEMENT TESTING. 

from I J to 3 times the tensile value, depending upon the length, 
dimensions, richness, age and method of treatment of the speci- 
men. For seven and twenty-eight day tests made on prisms of 
I : 3 sand mortar, one inch square and on a span of lo inches 
the factor is very nearly 1.5. If, therefore, a prism 7 or 28 days 
old be broken on this span the center load will be exactly one- 
tenth of the tensile strength. The procedure, therefore, is to make 
prisms 1x1x12 ins. of i : 3 sand mortar and to break them 
on a span of 10 ins. at 7 and 28 days, the center load causing 
rupture equaling one-tenth of the tensile strength in both cases. 
It is safe to assum.e that the average of 3 prisms will 
give a tensile value accurate to at least 30 per cent., so that 
if 170 and 240 pounds are specified for the tensile strength at 7 
and at 28 days, tests carrying a center load of less than 12 and 
16 pounds at these periods can be considered as doubtful, and 
those carrying less than 9 pounds at 7 and 12 pounds at 28 days 
may be rejected with comparative certainty. Although this may 
not ensure absolutely first-class material, it is far better than 
nothing and will positively preclude the use of worthless ce- 
ments. Xo apparatus, other than a pair of scales, is required 
except what may readil} be made with a few tools. 

Table LI. gives a series of tests made by the author to show 
the accuracy of rough tests made in this manner (Fig. 123). The 
values of tensile strength are the average of 3 briquettes, while 
3 prisms make the average for cross-breaking. It may be ob- 
served that the mean error of the prisms between them- 
selves averages but 5.3%, while the average error between 
briquettes and prisms amounts to but 5.6%. It is believed that 
this will be found the most satisfactory method for making ap- 
.proximate .tests of strength. 

Soundness. — The normal pat and boiling tests are recommend- 
ed for determinations of soundness, and their manner of conduct 
is exactly similar to that alread3' described in Chapter X. A 
paste of neat cement of normal consistency is made, and two 
circular pats about 3J ins. in diameter, i^ in. thick at the center 
and tapering to thin edges, and a round ball i^ ins. in diameter 
are formed. Enough paste will be left over from the setting 
test to make these specimens, so that only one mixing is re- 
quired for the two tests. The pats should be moulded on plates 
of glass about 4 ins. square and not less than ^-in. thick. 



APPROXIMATE TESTS. 



235 



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236 PRACTICAL CEMENT TESTING. 

The specimens, like briquettes and prisms, are kept in damp 
air for 24 hours, after which one of the pats is placed in water 
with the strength test-pieces, and the other kept in air protected 
from sunlight or excessive heat. These pats may be examined 
as often as desired, but sliould be kept for at least 28 days. Their 
condition is examined in accordance with the methods outlined 
on page 163. 

The ball for the boiling test, after having been kept 24 hours 
in moist air, is placed in clear water at normal temperature and 
graduall} heated so that the water is brought to a boil in about 
half an hour, and kept in boiling w^ater for 3 hours, after which 
it is removed and examined for checking or cracking. Any 
pail or can may be employed for making the test, the only points 
to be considered being that the volume of w^ater should be not 
less than a quart, and that some arrangement such as a bent 
piece of wire netting should be placed in its bottom to prevent 
the specimen from touching it. A second pail of water should 
be kept boiling beside the first, from wjiich water is poured from 
time to time to replace that evaporated : the addition of cold 
water may chill the specimen and afifect the results. Illustra- 
tions of samples passing and failing in this test are shown in 
Figs. 80 and 81. Cements failing in the normal pat tests should 
invariably be rejected. For the interpretation of the boiling 
test, see pages 175 to 182. 

Purity.* — For this test, provide a 4 ounce bottle of dilute 
(i : i) hydrochloric acid, a ^ ounce bottle of acetate of lead and 
a deep china or glass saucer. Place about as much cement as 
can be lifted on a quarter-dollar coin in the saucer and pour on it 
enough acid to cover it, stirring at the same time. 

Pure Portland cement effervesces violently for a second or 
two, leaving a residue of reddish jelly, which on the addition 
of more water goes entirely into solution except for a few flakes 
of silica. Adulterations of limestone, lime and natural cement 
effervesce much longer and generally leaves a residue of black 
gritty particles, which can be examined by adding more water 
to Ihe mixture, the cement going entirely into solution except 
for a few floating flakes of pure white silica, while the residue 
remains. Adulterations with cinder, sand, slag, or similar ma- 
terials also leave the gritty residue. The presence of slag may 

♦These as well as other tests for adulteration are described more fully in 
Chapter XL, page 204. 



APPROXIMATE TESTS. 237 

"be detected by the odor of hydrogen sulphide on the addition 
of the acid or by placing a strip of newspaper moistened in lead 
acetate over the saucer, which turns black or brown if slag is 
present. 

Apparatus. — The apparatus employed in the m.aking of these 
tests, determining strength in cross-breaking, is as follows : 

Postal scale — 4 ounces — J ounce. 

Pan scale — 30 pounds — \ pound. 

Sieve — 100 mesh. 

Glass graduate — 8 fluid ounces capacity. 

Linen-tester's microscope — J-in. opening. 

Small box of standard quartz sand (25 pounds). 

Six-inch pointing trowel. 

Six glass plates (4x4 ins.) 

Hydrochloric acid (i : i dilute) — 4 ounce bottle. 

Acetate of lead — -| ounce bottle. 

The other devices employed are such as may be obtained in 
any place, or which may be made with a few carpenter's tools. 
The cost of the articles in this list should not exceed ten dollars. 
For making the tensile test a small machine and a few moulds 
must be purchased, which will cost from 70 to 90 dollars, but 
which, for any one using much cement, is money well expended. 
Most engineers will already have all or part of the articles listed, 
so that the actual cost of apparatus is practically nil and at the 
same time the results of the tests give a very fair indication of 
the quality of the material and will always preclude the use of 
worthless or dangerous cements. 

Interpretation of Results. — The general interpretation of re- 
sults has already been considered at some length so will not be 
repeated here, but it is advised that the standard methods of con- 
ducting the tests as well as the conditions affecting them and the 
consideration of results be studied carefully before attempting 
to employ these cruder methods, so that just what reliance to 
place on them may be clearly understood. It would also be 
well, before making tests for the purpose of accepting or reject- 
ing a shipment, to examine some cements known to be good, 
and if possible, one of inferior ciuality, to obtain j)ractice in the 
conduct of the determinations. An unsound cement niav bo 



238 PRACTICAL CEMENT TESTING. 

prepared by adding from 5 to 10 per cent, of ground un-slaked 
lime to a iiormal cement. 

It is always safe to reject cement failing in the normal pat 
tests, and generally if failing in strength (less than 135 lbs. 
modulus at 7 days) or showing adulteration. Cement failing 
in boiling, fineness, setting, or giving a transverse modulus of 
less than 180 pounds at 7 days tested in a i : 3 mortar, should 
be regarded as suspicious and inferior to one passing these 
tests. 



CHAPTER XIV. 



PRACTICAL OPERATION. 



Equipment. — It is difficult if not impossible to give a list of 
apparatus for cement testing, that would entirely satisfy the 
needs of any particular laboratory and yet not include much un- 
necessary equipment. Each case therefore requires individual 
treatment according to the nature of the work and the demands 
upon the laboratory. The following Hst, however, is an attempt 
to give all the apparatus required by a large, fully-equipped 
permanent laboratory, or a field laboratory connected with con- 
struction of unusual importance. The outfit required for the 
testing connected with a mill, or with a fairly large piece of con- 
struction work may be obtained by omitting from the list those 
articles preceded with a star {'-■'). The quantities given are based 
upon a maximum testing capacity of eight samples a day, so 
that a greater or less estimated capacity will require alteration 
in the number of those articles marked with a dagger (f). 



I "shot" cement testing ma- 
chine (capacity 1,000 lbs.). 
*i "long lever" cement testing 
machine, with attachments 
for compressive and trans- 
verse tests (capacity 2.000 
lbs.). 
*i "universal" testing machine 
(capacity 150,000 lbs.). 
I scales for cement (1.500 

grams — i gram). 
I scales for fineness (100 
grams — o.i gram). 
*i scales for specific gravity 
(100 grams — o.oi gram). 
I pan scales for rough weigh- 
ing (50 pounds — 1 ounce). 
ti6 4 gang briquette moulds. 
ti6 3 gang briquette moulds. 
*t4 iron moulds for 6-inch cubes. 
*t4 moulds for 2-inch cubes. 
*t4 moulds for i-inch cubes. 
*t4 moulds for prisms (i x i x 

1.3 inches). 
*t2 moulds for prisms (2 x 2 x 
13 inches). 
I Vicat needle, with plun<icr. 



t8 additional rubber rings for 
Vicat needle. 

t4 No. 200 sieves for testing 
fineness. 

t2 No. 100 sieves for testing 
fineness. 
I No. 50 sieve for testing fine- 
ness. 
I each of No. 20 and No. 30 
sieves for testing standard 
sand. 

*i each of No. 10. No. 40, No. 
74 and No. 150 sieves for 
sand testing. 

*i each of sieves of oncnings of 
V\ ¥', f" and i" for stone 
testing. 

t2 "Le Chatelier" specific grav- 
ity bottles. 
I 6-inch funnel and stand. 

1 precipitating iar. 

2 each of No. 4 and No. 10 
beakers. 

2 graduates — 150 c. c. 

2 graduates — 350 c. c. 
*i graduated cylinder — l.ooo c.c. 
*i cubic foot meastiro. 
t2 chemical thermometers — 100* 
C. 



240 PRACTICAL CEMENT TESTING. 

I room thermometer. 4 6-inch scoops. 

I steaming and boiling appara- i sand glass (i or i^/l min.)- 

tus for soundness tests. i clock. 

I mixing table, or glass mixing J bag No. lo shot (25 pounds), 

slab (24 X 24 X ^ inches). t3 galvanized iron waste cans. 

cJ ^ 1 r^„ I Oil can. and motor oil. 

Storage tanks or pans for 6 brushes (assorted sizes), 

b^q^ettes. Bq^ Qf carpenter's tools. 

I damp closet. Glass rods and tubing. 

t250 glass plates— 4" x 4" x H • i each linen tester's micro- 

t8 glass strips (3 x I x length scopes (*" and i" opening) 

of damp closet). *i microscope (i-inch objec- 

I doz. — 6" pointing trowels. tive). 

I 3" pointing trowel. _ I 4" evaporating dish. 

6 pairs rubber gloves (with Bottle hvdrochloric acid 

gauntlets). (6 oz.). 

I doz. sink scrub brushes. Bottle acetate of lead (i oz.). 

i gross — marking pencils. Bottle methylene iodide (2 

fi barrel standard sand. oz.). 

*2 Bunsen burners. Bottle benzole (4 oz.). 

•t200 sample cans. fCan benzine (2 gallons). 

t3 collecting cans. Separatory funnel for testing 

I sampling auger. adulterations. 

In addition there must be provided tables, shelves, etc., as 
well as connections for gas, water and light. If a universal test- 
ing machine is installed, provision must also be made for power, 
preferably from an electric motor. A small fan motor should 
also supply power for operating the long lever cement testing 
machine. If it is desired to install an equipment for making 
chemical analyses, the list of apparatus required will be found 
on page 207. 

A simple equipment for a small field laboratory, testing not 
more than 2 or 3 samples a day, and only on specification re- 
quirements is contained in the following list : 

Cement testing machine (shot or spring balance). 

Pair scales for weighing cement. 

Pair scales for fineness. 

Briquette moulds. 

Mixing plate of glass 24" x 24" x J". 

Vicat or Gillmore needles. 

Sieves for fineness — Xo. 100 and No. 200. 

Sieves for sand — Xo. 20 and No. 30. 

Le Chatelier specific gravity bottle. 

Can of benzine. 

Glass graduate (200 c. c.) 

Thermometer. 

Boiling apparatus. 

Storage pans. 



PRACTICAL OPERATION. 



241 



Damp closet or arrangement for damp cloth. 

Glass plates (4"x4''x^")- 

Glass strips (3" wide — J" thick and suitable length). 

6" trowel. 

Rubber gloves. 

Standard sand. 

Sample cans. 

For making occasional or approximate tests, an extremely 
simple outfit has already been described on page 237. The four 
classes of equipment given represent the average of most test- 
ing laboratories, but every particular instance is so markedly 
different, that the necessary equipment is a very variable quan- 
tity, so that each engineer must decide what is needed to meet 
his own individual conditions. The different lists given, how- 
ever, may possibly serve as guides in this selection. 

Force. — To operate properly even the smallest of field 
laboratories, the testing should be performed under the direct 
personal supervision of a technically educated man, for it is 
only the man trained to making scientific observations who 
fully appreciates the importance of standardizing details 
and following them closely. It is seldom that even the best 
practical operators, when pushed for time, will not shorten 
the time of mixing or increase the rate of breaking briquettes, 
unless he knows that he will be called to account for so doing. 
It is not that the man is not conscientious in his work, but that 
he fails to appreciate the amount of error introduced by seem- 
ingly trivial deviations from the fixed method. The technical 
man, on the other hand, fully understands these conditions, and 
his only excuse for permitting work of this character is wilful 
neglect or carelessness. 

The number of men required to operate a laboratory, mak- 
ing the ordinary specification tests, will average one man in 
charge, and one helper for every four sami)les per day on the 
estimated capacity. Thus two men can rcadilx' test iouv samples 
of cement a day ; three men, eight sami)les, and so on. This, 
however, implies well trained and experienced operators ; green 
men will l)e fortunate to accomplish half ihis aniouni of testing. 
If it is desired to make chemical analyses. aniUher teclmically 
educated man must be added to the force. AIsd, if the daily 



242 



PRACTICAL CEMENT TESTING. 



amount of testing averages over 12 samples, it may be necessary 
to employ a clerk for recording and reporting the results. 

The salary of the man in charge will be from 60 dollars per 
month up, depending upon the size and importance of the 
laboratory and upon the amount of responsibility placed upon 
him. The salaries of the helpers will range from 30 to 75 dollars 
per month, while the services of a chemist will cost from 60 to 
100 dollars. 

The average field laboratory connected with construction 
work can be operated by two or three men, at a salary charge of 
from 100 to 200 dollars a month. A mill laboratory at a plant 
of about 1,000 barrels daily capacity making both chemical and 
physical tests can be operated by a chemist in charge and 2 or 
3 helpers, at a salary cost of about 200 to 300 dollars a month. 

Cost of Operation. — The cost of operation of a testing labor- 
atory is, of course, extremely variable, depending upon the 
number of samples tested, the number of tests made, the amount 
of experimental work performed in addition to ordinary routine 
and man}- other conditions, and hence may range anywhere from 
$1.50 to $10.00 per sample. Under the most favorable con- 
ditions a laboratory may reach the minimum figure given, but 
such cases must be infrequent. The cost of testing cement in 
the Philadelphia Laboratories, including salaries, supplies and 
repairs, but not including heat, light, power, rent or interest on 
money invested, averages from $2.00 to $2.50 a sample. 

The cost of a field laboratory on construction work will 
average from $3.00 to $5.00 a sample, roughly equivalent to 
about 3 cents a barrel of cement, or from 3 to 5 cents per yard 
of concrete, although it may average considerably in excess 
of this figure under unfavorable conditions. Even at a cost of 
5 or 6 cents a yard of concrete, the maintenance of a testing 
laboratory is tantamount to an insurance of tlie structure at a 
remarkably low rate. 

The cost of the original equipment will be anywhere from ten 
to ten thousand dollars in accordance with the amount and 
character of the apparatus. That employed in the author's 
laboratory would amount to considerably in excess of the maxi- 
mum figure. The list given on page 240 as a suitable equip- 
ment for a field laboratory should cost about $250, while the 
first complete list on page 239 would cost from $1,800 to $2,500. 



PRACTICAL OPERATION. 243 

A good outfit for a mill or large field laboratory could be pur- 
chased for about $350, or about $600 including apparatus for 
chemical analysis. Both the cost of equipment and mainte- 
nance are therefore seen to vary between ^vide limits, depending 
upon the particular conditions to be met, but the foregoing 
will serve as a rough guide for the estimation of cost in any 
individual instance. 

Operation. — Probably the most important factor in the 
efficient operation of a cement testing laboratory is in the em- 
ployment of experienced and conscientious men. Xo mattei 
how carefully a standard method of manipulation be followed, 
an inexperienced operator will at first obtain most inaccurate 
results, and the only way to train him properly is to rec|uire 
him to work day after day beside an experienced man and from 
the differences in the results learn where to locate his errors. 
Most of the operations of cement testing ma}- be learned after 
practice of a week or two, but the proper making of briquettes 
cannot be acquired in less than a month's hard work under in- 
telligent supervision. If it is necessary to employ a green man, 
on first organizing a laboratory, the results of his early tests 
should be interpreted witli a large provision for error. The 
uniformity of his work may be tested by computation of the 
probable or average error of his results, but systematic errors 
can only be detected by most careful supervision and by ct^m- 
parison of the values obtained with those of a well-established 
laboratory. Where the force consists of several men. it is also 
advisable to have trained under-studies for each man's work, so 
that in case of any one man's sickness or retirement another 
can take his place without the confusion attending the breaking 
in of a new man. 

Another advisable procedure is to have printed or tvi)c- 
writtcn copies of the standard methods of testing in the hands 
of each operator, and to make certain that he is eniireK lamiliar 
with all the steps of the process, and understands the imi^ortancc 
of adhering to every detail. A wilful vi(il:'.tic>n or departure 
from the fixed methods to gain time or to make the work easier 
should result in his instant dismissal from the force. Tlie dif- 
ficulty of instilling tlie importnnce of d.etail in the minds o\ prac- 
tif^al but uneducated men makes inmerativi- the constnnt super- 
vision of a man of scientific training, for i)ther\vise the character 



244 



PRACTICAL CEMEXT TESTING. 



of the work soon becomes so slipshod that the results of the 
tests are almost valueless. 

In formulating a standard method of testing, the great dififi- 
culty lies in determining the line where economy of time and 
labor at the expense of accuracy must stop, the only proper 
method being first to learn wdiat accuracy is essential to the cor- 
rect interpretation of each test, and then to ascertain whether 
the probable error or best the maximum error of the methods 
lies within that limit of accuracy. Thus, in the author's labora- 
tory it is the practice to remove briquettes from the damp closet 
after 21 instead of 24 hours, it first having been learned that this 
departure from standard practice had no appreciable influence 
on the results, while at the same time it much simplified the day's 
routine. The time of mixing briquettes also has been shortened, 
to economize labor, to one instead of i^ minutes, the uniformity 
and accuracy thus obtained being still well within the allowable 
limit of error, but mixing for only half a minute was at the same 
time found to create errors of unjustifiable amount. Thus each 
step in the process should be considered and the best method 
adopted. 

Another important detail necessary to obtain accuracy, is the 
systematic recording on regular forms of the results of the tests, 
made immediately after each determination. Alany operators 
jot down their figures on a slip of paper or the back of an en- 
velope, and then copy them after all the tests are finished, which 
is likely to cause the making of mistakes, and often creates a 
tem-ptation to slighth alter the figures if the values are obviously 
abnormal or show much error. The author once saw an operator 
m a well-known laboratory break briquettes at values of say 238, 
300, 254, 288, and then record say 264, 275, 270, 271, saying "it 
is just the same thing, and it looks better, you know." This 
tendency of operators to make their reports look better is 
largely overcome by requiring each value to be entered on a 
printed form immediately after each result is obtained. 

Three of the laboratory sheets used by the author are shown 
in Figs. 124, 125 and 126, these being for fineness, setting and 
briquette reports. Similar sheets are used for pat tests, boil- 
ing tests, specific gravity and the other determinations. 

Recording Systems. — Different methods of recording and re- 
oorting the results are of course necessary to meet different 



PRACTICAL OPERATION. 



245 



TESTINQ LABORATORY 

FINENESS TESTS 



No. 


50 


100 


200 


J-V2 70 


^. ^ 


7.3 


■z.'/. r 


1./ 


0.0 


s. ^ 


T-3.^ 


-?jr 


a.^ 


r.^ 


^6.^ 


7^ 


a.o 


^.^ 


24/^ 


77 


a. d 


/i. s 


-T-^.a 


1^ 


a. a 


/; 


^'/.r 


-y? 


^. 


9. ^ 


2 ^ ^ 


J^a 


0. / 


^. /• 


■^3.6 


A-/ 


0. 


7.x 


•2.A<a 


^Z- 


a a 


J~^ 


-L-i.& 


^3 


a. a 


^.0 


■2.3.0 


,fV 


a. a 


-7. ^ 


■2,3 y 


/J- 


a.o 


4^/ 


7- a. 6 


J-^T-f^ 


a. a 




z «<^ 















lA/... /!^.._... 

Fig. 124. — For Fineness Tests. 



TESTING LABORATORY. 

CEMENT BRIQUETTES. 

/o-j'-aJ' 



Age 


No. 


1 


2 


AVc 


2^^ 


S3'? 7.^ 


^6 r 


r^3 


^aj- 






30 7 


0/0 


J09 




3a 


ys-^ 


■y/o 


7'^7 






^cf^ 


zf/ 


z/^ 




/ 


-7S-3 


76 7, 


is-r 






3 


^9^/ 


^97 




J'2- 


6^9 


6J^ 


6^^/ 






7.3 J>- 


X V/ 


) 






UJ^^ 


7.'/3 


- 2.4/<5' 




33 


<(■£></ 


7cP/ 


193 






J /^ 


3/,i- 


a/j~ 




jr39J^ 


7J-^ 


-7^^ 


i^-r 






■z.-y JT 


Z7/ ■ 


7-73 

































c. //. ^. 
Fig. 126. — For Cement Briquettes. 



TS^STING IvABORATORY 



8EX XE»X 



/O - 3 - ^s- 



No 


Brand 


% 
Water 


Time of Setting 


Paste 
Temperature 


Room 




Beein 


Init. 


Hard. 


Temperatur< 


^-/z^^ 


^ 


/-^ 


^-DC 


//-as- 


^-2^ 


1- 1 


2V 


zt 


T.^ 


-//) 


/3 


/9.0 


9-3d- 


//-^^' 


J - /^ 


-2. 1 


7-y 


X -z- 


1^ 


7/ 


C 


1^0. 


9-^0 


/0-a9 


// ~oy 


X / 


^f 


■2. -L 


-UU 


7i 


JJ 


■LO.^i- 


^--/-Z 


/a-J-J- 


:l-VO 


z/ 


^7 


Z X. 


•2. J" 


7.-3 


cf 


/f.^ 


9-V9 


/T. -ay 


A^ -ao 


-z. / 


2 :» 


2- -2. 


^.1 


?/ 


7^ 


/^J- 


^-J-^ 


// -oa 


V - /o 


2- / 


1-6' 


■Z^Z, 


2J 


7^" 


^■~ 


•2./. 6) 


9-^9 


J/ -o<^ 


J- ay 


•2. / 


7.6 


-2. -2- 


-r-V 


7^ 


A/ 


/9.^~' 


/o-o:} 


/a- j's 


3-ao 


X / 


■^•>' 


i-z- 


T.^ 



c. /y. i;.. 



Fig. 125. — For Tests of Time of Settiii}:;. 
LABOR ATOkV KICPOKT SHEETS. 



246 PRACTICAL CEMENT TESTING 

conditions, bnt it is thought that a description of those used in 
the Philadelphia Laboratories, where a large variety of materials 
are tested for use in many classes of construction, may be of 
interest. After experimenting with several systems of record- 
ing, including record books, loose-leaf books and card-systems, 
it was found that the last method was far more convenient than 
any other. A mill laboratory, or one in the field where only one 
brand of cement is tested for but one piece of construction, may 
use ledgers to advantage, while where several brands are used 
the loose-leaf books may be employed, but for the average 
laboratory the card system will be found the most convenient 
and satisfactory in the long run. They may be indexed in any 
wa} , may be referred to with great ease, while for obtaining 
average results or for examining the properties of any particular 
brand among those tested, the amount of time and labor saved 
is very marked. 

The following is a description of the methods employed in the 
Philadelphia Laboratories for recording and reporting results : 
Whenever a shipment of cement is received upon any municipal 
w^ork, the field inspector sends to the laboratory a postal card, 
on which is stated the size of the shipment, the brand of the 
cement, the place received and the character of the work for 
which it is intended. On receipt of this notification a collector 
is sent to the work, who not only takes a sample of the material 
in accordance with the methods given in Chapter V., but also 
examines the shipment as a whole in regard to its condition, the 
soundness of the packages and its storage, a report of which is 
submitted with the sample. These samples are brought to the 
office, placed in sample cans, which are marked with a con- 
secutive number and the notification card given the same num- 
ber and filed. The sample is henceforth, during the progress 
of the tests, known only by its number, so that, even if it were 
so desired, it would be impossible for any operator to show 
favoritism to any sample or brand in the conduct of the deter- 
minations, the author making a point of marking the samples 
personally. 

After the samples for each day's testing are marked, a dis- 
tribution sheet (Fig. 127) is made out, giving the number of 
briquettes to be made from each sample and the ages at which 
they are to be broken, it being assumed that 7 and 28 day tests 



PT^ACTICAL OPERATION. 



'2X7 



TESTING LABORATORY 

DISTRIBUTION SHEET 



No. 


Age 


Remarks 


j-^zyj 


Z-^. 




7^ 


4- ^ 




7J- 


^ _ 




-76 


/ ^.^ 




77 


^-y-^- ./«^ 


/<Z ^ - /;? _ 


iSr 






'7f 


C5-^^ 




/^ 


r 

Z-6^. /u^ 


/ Z -pi. - /^.r 


// 






/Z 




-7 .^ 2^ ^z^ 




^.7 


^-^. 




^ 


6^^. 




J-^- 


3 v<<.» 




j-'/zJ'6 



















cf: ^, ^^ 

Fig. 127. — Distribution Sheet. 



TESTING LABORATORY 



8REAKINS SHCCT 



A«e 


Briquettes 


7 Days 


j-'^/jo M. j-4^/9^4/ 


28 Days 


J~3 9/2. A> ^391-S^ 


2 Mos. 


S-3-73 / 


3 Mos. 


J- J V z f - J y -a o" V :2i_ 


4 Mos. 




6 Mos. 


S'-z.'/ 3 6 - V/ 


' 1 Year 


d-a^^-f- 9^-'F9 


2 Years 


^79 S^<^ 


3 Years 




5 Years 


4^Z7<^/- <6->"- / ^ 


7 Years 




10 Years 




y /pc^xa^^. 


JW^^zv^ - a.£.- /X,^ /3. 


/ 


' 






^ 





Fig. 128. — Breaking Sheet. 



NUMBER 






BRAND 








DATE TESTED 




^^^ ^.2^ 


/ PLACE OF COLLECTION 


Date CoyiECiED 


Fineness 


60 

0.0 


100 
7 cf 


200 II 
__ - SPECIFIC GRAVITY 


3./^^ 


Setting 


INITIAL 


HARD 


RISE 

C7 


TEMPERATURE 

z/ - -^Z 


','; WATER 

-2-0. S" 


Strength 


Id. 


/77 


70. 


7^r 


280 


^;i'3 


.? 


<irS-& 




1 : 3STA. SAND 


70. 


Z/^i' 


280. 


3a ^ 


-W. 


ZTZf 


Pats 


■ air:7d. 
r/-S 1 


AIR.!/SO. 


WATER-70. 


WATlR-380. 



Remarks : 



^^ - /?/ 7P- 7 2 C7^^. 



^^- /c; /Y. c 



/sjiTiZi^ J-ut//- - ^^r^ 



-vT^ , - /^ r 



Fig. 129 —Card Record Used in the Philadelphia Laboratories. 



248 



PRACTICAL CEMENT TESTING. 



are always made, while, If not otherwise stated, the number 
of briquettes is taken to be eight neat and six sand. At the 
same time, the briquettes to be broken at each period are en- 
tered in diaries arranged 10 years ahead, so that they show for 
each date exactly what tests are then to be made. For example, 
if briquettes are put up on Alay i, 1905, to be broken at 7 and 28 
davs, 3 months and i year, the sample number is entered under 
May 8th, May 29th, August ist, 1905, and ]\Iay ist, 1906. 

After the briquettes have been made, and on the following day 
removed from the moulds and marked, they are placed in the 
storage tanks, which are divided by sections into periods of i, 
7 and 28 days, 2, 3, 4 and 6 months, and i, 2, 3, 5, 7 and 10 
years. With the distribution sheet as a guide, each briquette 
is placed in the section marked with the age wdien the test is 
due, those in each section being placed in the order of making, 
so that the beginning of the first row contains the first briquettes 
to be broken. Each day a breaking sheet (Fig. 128) is copied 
from the diary giving the tests due on that date ; with this sheet, 
the operator breaking the briquettes can go to each section of 
the tanks and remove the first briquettes in the different rows, 
whose numbers should correspond with those on the sheet, thus 
avoiding any waste of time in hunting for the different 
briquettes, insuring that every test is made on the proper date 
since by this method it is impossible to overlook them, and also 
requiring a minimum storage capacity in the tanks. Of course. 
for handling a small number of briquettes, so elaborate a sys- 
tem would be unnecessary, but when, the briquettes in storage 
run well into the tens and twenties of thousands, the lack of such 
system means much wasted time and energy. Xo matter how^ 
few tests are made, the use of diaries, in which, under each date, 
are entered the tests when due, will be found most convenient. 

When any determination is made, the results are at once en- 
tered on blanks similar to those shown in Figs. 124 to 126, 
eight different forms being employed in routine cement testing, 
all of which are sent to the laboratory office twice a day for 
entry. The permanent records consist of a consecutive num- 
ber book and a file of card records. In the consecutive num- 
ber book are entered, when each sample is received, its num- 
ber, the size of shipment, the number of the car (if in car load 
lots), the place and nature of the work where it is intended for 



PRACTICAL OPERATIOX 



249 



use, the date received, the date tested, the brand of the cement, 
the number of briquettes made and the periods when the tests 
are due. From this data the first two Hues of the card (Fig. 129) 
are made out, while the other spaces are filled from the labor- 

(OFFICIAL HEADING) 
Tke following are results oj tests oj 

samples of cement ivtended for use 



Place of Collection, 




















Brand. 










Number of Car. 










Specific Gravi/v, 










fineness: 










t % Residue on No to Sieve. 










" " " " /OO " 










M .. " •' 200 •' 










TIME OF setting: 










, Initial Set {in minutes). 










, Hard Set ' 










TENSILE strength: 










34 hours, neat. 










7 days. 










28 days. 










, 7 days. parts sta. sand. 










jS days, parts sta. sand, 




















Boilinsr Test. 









Remarks: 




Report appro7'ed. 


Respectfullv sul^mitled. 




Chief Engineer, 


. . En^iMetr of Tests. 



Fig. 130. - Report of (\>nu>nt Tests. 

atory sheets as thcv arc reported, the sheets themselves beinpf 
filed for possible future reference. ( >nly the average strength 
is recorded on the card, while a special notation is emplo\ ed for 
the pat tests, \'. S. C Lg. slantling for very slightly curled, left 
glass, etc. The cards for natural cement are similar, except 
that the strength is tested with 2 instead of 3 parts of sand, and 



250 



PRACTICAL CEMEXT TESTIXG. 



>■ 

>- 
cc 
O 

< 

z 1 

y: 

1 

d 

ZL 

V 
■J'. 


— 


= 






' 






- 






- 






f. 






- 


li 1 




i 


= 


1 1 




' 


II 


M' 




= 


1 ' 


Ml 




" 




, III 




a 
1 


3 


ill II 








^ 






- 




M II 


i 


•1 








i 

1 


3 




i • f 1 1 




1 






1 


1 


■\ ill; 




1 






11 


1" 


{ill liii 1 




j 


1 






' 


1 




II 11 


1 


S 


1 i 




«i^ 




1 


Jl 




i\ 



PRACTICAL OPERATION. 251 

are of buff color, while the Portland cards are white. They are 
filed in rotation until the 28 day tests are made, after which they 
are cross-indexed and filed by brands and by the periods when 
the "long-time" tests are due. 

Reports as shown in Fig. 130 are made at the expiration of 7 
and 28 days, any values failing to meet the requirements being 
stamped with a red star. As an aid to averaging the results 
for the annual report, and also to enable one to examine 
rapidly the run of an} particular brand, it has been found con- 
venient to employ balance sheets (Fig. 131), on which the values 
are entered after the 28 day tests have been recorded, and the 
total value of each column, with the number of tests comprising 
it, completed on each sheet ; with these sheets it is possible at 
any time to obtain the average of the results of any brand within 
a few minutes. 

The records of experimental tests and investigations, as well 
as of special tests not in regular routine, are kept in ordinary 
record books, the subjects being indexed on the card system. 

This system has been evolved after the experience of almost 
15 years in handling a great variety of many materials under 
varying conditions, and has been proven the most convenient 
and satisfactory of the many systems tried. 



CHAPTER XV. 

NATURAL, SLAG AND OTHER CEMENTS. 
NATURAL CEMENTS. 

Natural cements are those made by the burning and subse- 
quent pulverization of an argillaceous or argillo-magnesian lime- 
stone, and, as the name implies, are made from a single variety 
of natural rock, without previous pulverization or blending with 
other materials. In burning the heat is never carried to clink- 
ering temperature. 

These cements are made from materials of widely variant 
character and composition, so that the characteristics of the 
different varieties bear little similarity to each other. The two 
best known groups of this material are the "Rosendale" and 
"Louisville," both of which, however, include several brands of 
more or less varying composition. These group names are 
often incorrectly used to cover the entire class of natural ce- 
ments. 

Production. — Natural cement was first produced in the United 
States in the year 1818, six years prior to the date of Aspdin's 
patent on Portland cement and 57 years before it was made in 
this country. The first works were near Fayetteville, N. Y., 
and large quantities of the product were used in the construc- 
tion of the Erie Canal. The growth of the industry may be seen 
by reference to Table L, page 4. It will be observed that for 
the past 12 to 15 years the production has remained practically 
constant, this being due to the great increase in the popularity 
and use of Portland cement. The production by states or dis- 
tricts is shown in Table LIL, the New York or "Rosendale" 
district, leading in both number of mills and amount produced, 
with the Indiana-Kentucky or "Louisville" district second. 

Manufacture. — As compared with Portland, the manufacture 
of natural cements is a very simple process. The raw rock is 
either mined or quarried and conveyed to the works in sizes 
from a "two-man" stone down. Some of the better mills make 
a practice of running all the rock through a crusher of the Blake 
type to secure some uniformity in size, but most burn the stone 
as quarried, without any preliminary treatment. 



NATURAL, SLAG AND OTHER CEMENTS. 



253 



The rock is burned in plain vertical cylindrical kilns (Fig. 
132) made of stone, brick, or iron, lined with fire brick, and 
operating continuously. The dimensions of the kilns vary 
greatly in different localities, depending on the rock, the fuel 
and various other conditions, but usually are from 30 to 45 feet 
in height and from 8 to 16 feet in diameter, the lower 5 or 6 feet, 
tapering to a reduced section. Both anthracite and bituminous 
coals are employed in the burning. The rock and fuel are fed 
into the top of the kiln in alternate layers, the amount of fuel 
averaging from 10 to 20 per cent, of the weight of the rock, while 
the temperature maintained in the kilns varies from 700° to 



TABLE LII. 



State 



■Production of Natural Cement in 1903, by States. 
(From Mineral Resources, 1903.) 

Number 
of Works 



Georgia 

Illinois 

Indiana and Kentucky 

Kansas 

Maryland 

Minnesota 

New York 

North Dakota 

Ohio 

Pennsylvania 

Texas 

Virginia 

West Virginia 

Wisconsin 



Total. 



2 

3 

15 

. 2 

4 

2 

20 

, 2 

7 
2 
2 
I 
2 

65 



Quantity 


Value 


Barrels 




80,620 


$44,402 


543.132 


1 78. 900 


1.533.573 


765, 786 


226,293 


169,155 


269.957 


138,619 


175,000 


7^,750 


2,417,137 


1,510,529 



67,025 

1,339.090 



47,922 



330,522 



7,030,271 

(a.) Includes product of North Dakota and Texas. 
(b.) " " " West Virginia. 



46,776 
576,269 

25 961 

139,373 
3.675.520 



1,000° C. The burning is continued until most of the carbonic 
acid is driven ofif, and until the rock is porous and friable, and 
when complete the material is drawn from the bottom. 

On account of the inability to control the burning exactly, a 
part of the material is overburned and some undcrburncd, thus 
requiring sorting; the overburned material is often discarded, 
while that insufficiently burned is given a second calcination. 

The first step in the process of grinding is generally to run 
the calcined stone through a rough crusher known as a "pot 
cracker" (Fig. 133), which consists of an iron cone, revolving 
in a shell of similar shape, both surfaces being i^rovitled witii 



254 



PRACTICAL CEMENT TESTING. 



corrugations. The process then varies greatly in different mills, 
in some it is screened, the coarse material returning to a finer 
cracker or edge-runner mill, others send all the material to the 
fine grinders. These last mills are usually of the old buhr- 
stone type, 3 to 5 feet in diameter. Emery mills are also em- 
ployed and often are more economical. A second screening 
is made in many plants after these mills, the coarse material 
returning again to them. 

In some works, tube mills are employed for the fine grind- 
ing; others have batteries of rolls and Griffin mills, or Kent 




Fig. 132. — Kilns for Burning Natural Cement. 



and tube mills. Disintegrators with tube and Griffin mills are 
also used. The calcined natural rock, on account of the lo\ver 
heat of burning, is much softer and hence easier to grind than 
Portland clinker. Figure 134 shows a cross-section through 
a mill grinding with crackers and buhr-stones, and which is 
typical of the ordinary natural cement plant. 

The finished cement is seldom stored in bulk, but is packed 
in bags or barrels as soon as it comes from the mills. The 
net weight of a barrel of natural cement averages 280 pounds, 
3 bags being the equivalent of a barrel. 



NATURAL, SLAG AND OTHER CEMENTS. 



255 



The chief difficulty in the manufacture of natural cement lies 
in the variations due to the differences in composition between 
the different strata of rock. This is controlled to some extent 
by blending in the quarry, and again, in many mills, by a thor- 
ough mixing of the finished cement, but even the most thor- 
ough precautions will never ensure an absolutely uniform pro- 
duct, and it is this condition that constitutes the chief objection 
to this grade of material. 

Composition. — The composition of a number of varieties of 
natural cement is shown in Table LIII. It will be observed that 




Fig. 133.— Pot Cracker. 

the content of silica, magnesia, alkalies and carbonic acid is 
higher, while the lime is considerabl\- lower than in PcM'tland 
cement, thus giving a higher hydraulic index. 11ic burning re- 
sults in the forming of man)- complex silicates and aluminates. 
as well as substances of a pozzuolanic character, but unlike 
Portland this material admits of the formation of many com- 
pounds without materially altering its characteristics, whereas 
all Portland cements are essentially of the same composition. 
Another lack of similarit\' between naturals and Portlands is 
that the content of magnesia in tlu- lonner acts in a ver\ dif- 



256 



PRACTICAL C EM EXT TESTIXG. 

















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NATURAL, SLAG AND OTHER CEMENTS. 



257 




258 PRACTICAL CEMEXT TESTIXG. 

ferent manner and may be present in considerable amount and 
used in the most unfavorable conditions without injury to the 
structure. An example of this is in the foundations of the 
"Brooklyn Bridge" in Xew York, the masonry foundations of 
which are laid in a mortar f natural cement containing over 
20% magnesia. 

Color and Weight. — The color of natural cement is much va- 
ried — ranging from a light yellow, to dark gray and even to a 
chocolate brown. Generally the color is no criterion of quality, 
except as a measure of the uniformity of a single grade of the 
material. 

On account of the much lower heat in burning, and hence 
the less complere combination of the ingredients, the weight 
of natural cements is much less than that of Portlands, being 
about 45 to 65 pounds per cubic foot against 70 to 90 pounds 
for Portland, in a loosely filled measure. 

Specific Gravity. — The composition, and hence the degree of 
burning, of natural cements is so variable in character that the 
specific gravity is generally no criierion of quality regarding 
the class of material as a whole, but as a measure of the uni- 
formity of a single grade, the test has some slight value. Age 
and dampness tend to reduce the specific gravity, as with Port- 
lands. The method of conducting the test is similar to that 
already described, while the results will range from 2.70 to 3.00. 

Fineness. — The degree of fineness to which natural cemen: is 
ground depends both upon the composition of the material and 
upon the grinding process employed. ^laterial reduced on 
buhr-stones will usually have a much larger percentage of very 
coarse particles than tha: ground in tube or GrifiBn mills. The 
percentage passing a Xo. 200 sieve averages nearly the same 
as Portland, although the ratio between the residues on the 
different sieves is much less constant. For example, the fol- 
lowing represents the average of many tests of two brands of 
natural cement tested in the author's laboratory, the first be- 
ing reduced on buhr-stones and ihe second in tube mills : 



Xo. I 
Xo. 2 



Sieve 


Sieve 


Sieve 


Xo. 50. 


Xo. 100. 


Xo. 200. 


2.4 


12.6 


21.8 


0.1 


47 


21.3 



NATURAL, SLAG AXD OTHER CEMEXTS. 



^59 



Cement testing less than 15% on the Xo. 100, and 30^^ 
on the Xo. 200, may be considered acceptable. In general, the 
effect of fineness on setting and strength, and the method of 
conducting the determination is similar to that already given for 
Portland cements. On account of the lower lime content, how- 
ever, fine grinding is not as essential to soundness with this 
material. 

Time of Setting". — The setting of natural cements is also very 
variable, but generally is much quicker than Portland, although 
slow setting naturals are not infrequent. One characteristic 
of the setting of natural cements is that the ratio of initial to 
hard set is much greater than with Portlands, the hard set fre- 
quently occurring within 15 minutes after an initial set which 
required 15 or 20 minutes to develop, while a Portland cement 
acquiring initial set in that time generally requires about 2 or 
3 hours, and even longer, to set hard. The effect of age on 
setting is generally less marked with naturals than with Port- 
lands, the effect of fineness is very similar, while the effect of 
varying precentages of water is usually more decided with this 
material. 

The normal consistency employed for this test is similar to 
that for Portlands, but a much greater percentage of water is 
necessary, ranging from 23 to 35 per cent., depending upon the 
composition, fineness, age, and other conditions; otherwise the 
method of testing time of setting is similar to that given in 
Chapter VUJ. Specifications usually stipulate that it shall not 
acc|uirc initial set in less than 10 minutes, nor hard set in more 
than 5 hours. 

Tensile Strength. — The methods and processes of testing the 
tensile strength of natural cements are similar to those em- 
ployed for the testing of Portlands, except that there is far less 
uniformity of practice in regard to the proportions of the sand 
mortar specimens, t : t, t : 2 and i : 3 mixtures all being used 
by different laboratories. The i : 3 mixtures have thc.objection 
of being so weak when removed from the moulds that they fre- 
quently are sj)oiled in handling, and also so low in strength at 
7 days that it is difficult to obtain accurate results. Mixtures 
of I : I, on the other hand, are too rich to have the typical {prop- 
erties of sand mortar. T^'or these reasons, it is advisable to 
test natural cements in a mixture of one part of cement to two 



26o PRACTICAL CEMENT TESTING. 

parts of sand, this mixture containing enough aggregate to 
be characteristic of sand strength, and >et strong enough to 
handle easily, and test accurately at 7 days. 

The strength of natural cement is much more regular in its 
increase with age, and the curves of hardening seldom show 
retrogression in the strength of either neat or sand tests, in fact 
any retrogression may be considered as indicative of injurious 
properties. The effect of age on the cement is to lower gradu- 



TABLE LIV.— Effect of Varying Percentages of Water on the Strength 

of Natural Cement. 

(Tests from Paper on the "Tensile Strength of Cement," by E. S. Earned, 

Proc. Am. Soc. Test. Mats., 1903.) 

Water ' Sieve test: 

Brand ^i^- K„/«^kr%o. 



cent. 



50 100 180 



23 O.I 4.6 10.2 

25 
27 
29 
31 

33 
35 
37 
39 



B 23 2.3 12.4 21.9 

24 
25 
27 
29 
31 
33 
35 
37 
39 



. Wire: > 

minutes 


24 


Tensile Strength 

7 28 3 6 


12" 


Light Heavy 


hours 


days 


days 


mos. 


mos. 


mos. 


13 


32 


212 


251 


252 


311 


275 


3.S6 


18 


39 


185 


218 


215 


289 


300 


341 


21 


42 


150 


188 


220 


257 


272 


314 


20 


52 


128 


178 


202 


246 


248 


256 


21 


57 


112 


173 


199 


224 


259 


309 


27 


8S 


104 


172 


182 


267 


246 


290 


3« 


137 


93 


121 


178 


260 


286 


319 


34 


160 


85 


108 


168 


262 


3c6 


326 


67 


233 


«5 


119 


202 


252 


371 


400 


22 


59 


138 


177 


271 


332 


284 


264 




78 


125 


141 


264 


342 


309 


310 


35 


120 


150 


164 


216 


308 


318 


321 


49 


143 


117 


lib 


194 


305 


345 


272 


76 


166 


96 


105 


164 


272 


320 


267 


117 


212 


72 


72 


159 


270 


371 


225 


"5 


235 


62 


71 


147 


277 


379 


244 


127 


400 


50 


64 


112 


245 


318 


315 


198 


828 


59 


62 


96 




284 


351 


260 


1057 


54 


56 


85 




355 


364 



Note.— Each value is average of six briquettes. 



ally both its early and ultimate strength until finally the ma- 
terial possesses Httle if any cementing properties, although it 
is always somewhat active as a pozzuolanic material. The ef- 
fect of the use of different amounts of mixing water is generally 
greater in natural cements, as may be seen from Table LIV., 
taken from the same source as Table XXXI. The effect of 
fineness and of the character of the mixing sand is mechanical 
in action and, therefore, is similar in both naturals and Port- 
lands. In general, the efifect of exterior conditions, is prac- 



NATURAL, SLAG AND OTHER CEMENTS. 



261 



tically similar for both grades of material ; the conduct of the 
test is identical, except for the employment of the richer sand 
mixture. The normal consistency is obtained with much great- 
er ease by use of the ball method than with the \'icat needle 



800 1 M 1 M 1 1 1 1 1 1 1 1 1 1 1 1 1 M 1 1 1 


' ---y--^- ■■, 


-J-1800 




- . - : : : 1. 4: _ 4: 


qi 














































: . .± _ : ± _:._ 
























1 












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Jl - 1 - -T - - 






1 1- . • .± 






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_u.30O 




-HFAT-NATUB^j£^^l-- ^-^^^:^^r-----z^ 


:::::::: I : IP: ]53lQ=ir4= 


^— — r — ,r. ,_M R T A B-- i 


—^200 




— — - 1: 2HV10R-TAR — 









inn ^^ ''^ipr^^ — ^~rrrM"-ix-;-^n"i 


' '" " r "" \ ' '^" \' ' 


_^-. 














T 1 




- 1 


1 : , 


""1 " : , , i , , 



: MOS. 3 MOS. 4 MOS. 6 MOS. 8 MOS. 10 MOS 12 MOS, 

Fig. 135. — The Strength of Natural Cement. (From Taylor and Thompson's 
" Concrete — Plain and Reinforced.") 

for the quick drying out and early setting of the specimen 
make the latter determination difficult for this material. As 
with Portlands, the ball method consistency plus one per cent- 
gives very closely the Vicat needle consistency as recom- 
mended by the Committee of the American Society of Civil En- 



i 500 

JZ 

D)C400 
fli cr 

^;:?3oo 

°"200 



a> if) 



i~ 



100 









__± — . _i _±..±.. 


z::::::z:zzzzz::z:::::z:i,,^h 


::::::::::;;: = ?■:"'::::: ::--:::::::::;:::; = !!::::::::::::::::::::: :::::::::: 



























500 



30O 
100 



I 7 S8 
,K-Days-H< — 



4 6 
Months 



,8 



Fig. 136. — The Strength of Natural Cement. ( From Tests by the Author.) 

gineers. The percentage of water for sand niixtin-os is given 
in Table XXXIIL, page in. 

The average strength of natural cements is shown in I'igs. 
135 and 136, and a comparison with the similar curve for Port- 
land cements (Fig 79) shows the rate of hnrdiMiing to be nmch 



262 PRACTICAL CEMUXT TESTIXG. 

more uniform and regular. A good natural cement should de- 
velop a strength of 125 pounds at 7, and 22z^ pounds at 28 days, 
tested neat, and 75 and 140 pounds at the same periods when 
tested with two parts of standard quartz sand. When Ottawa 
sand is employed, the sand strength requirements should be in- 
creased 20 or 25 per cent., or to 90 and 170 pounds, respec- 
tively. Any retrogression in strength between 7 and 28 days 
in either neat or sand briquettes is usually indicative of future 
tmsoundness, and such action should always cause the rejec- 
tion of the shipment. The strength of natural cements is, on 
account of the less perfect control in manufacture, much more 
variable than in Portlands, even in different samples of the same 
brand. Generally those developing the best increase in strength 
between 7 and 28 days give the highest tests for longer periods, 
although there are frequent exceptions to this rule. ^^laterial 
passing the above minimum specifications and developing an 
increase of over 20% between the two periods will, however, 
be sufificiently strong for all ordinary purposes of construction. 

Soundness. — Norma] tests, or those made on pats of neat ce- 
ment paste kept in air and water, are considered to be the only 
conclusive tests for the soundness of this material. The tests 
are made, and the specimens examined in accordance with the 
methods given in Chapter X. Natural cement pats in air sel- 
dom adhere to the glass plates, while those in water adhere 
even more strongly than Portlands. This adherence to the glass 
plates, however, is no criterion of quality. Excessive expan- 
sion, checking, or disintegration in normal pats, is similar in 
efifect with both natural and Portland cements. 

Accelerated tests for soundness have frequently been tried, 
but the consensus of opinion seems to be that their results are 
misleading and inconclusive. ]\Ir. Sabin"^ states that compara- 
tive tests on briquettes of sand mortar kept in water at 80° 
C, and at normal temperatures, give a fair indication of the 
ultimate strengths attained. Tests on pats kept in hot water 
of a temperature of from 40° to 80° C. have also been advo- 
cated, but their employment is infrequent. In general, it is 
sufficient to emplo}' the normal pat tests alone for natural ce- 
ment, both on account of the unreliability of the accelerated 
tests, and also because of the fact that unsoundness as a rule 

•In "Cement and Concrete," by L. C. Sabin. 



NATURAL, SLAG AND OTHER CEMENTS. 263 

develops much more quickly in naturals than in Portlands, 
usually within 28 days. 

Chemical Analysis. — Except in the mills, analyses of natural 
cements have practically no value as a guide to their quality, 
except, possibly, that a measure of the degree of burning may 
be obtained from the content of carbon dioxide. Methods for 
chemical analysis, however, have been given in Chapter XL, 
page 191. 

Rough Tests. — For making rough approximate tests of nat- 
ural cement, as outlined In Chapter XIII., the same methods 
should be followed except for the omission of the boiling test, 
and the test for purity. 

For the fineness test, 85% should pass the No. 100 sieve. 
The setting cakes are mixed with from 23 to 35 per cent, of 
water, as may be necessary to produce normal consistency, and 
are examined after 10 minutes and 5 hours. Tensile tests are 
made on neat cement and i : 2 mortar, and should develop the 
different strengths just given. Transverse tests also follow the 
same methods and are made on both neat and sand specimens, 
and the results interpreted as for Portlands, allowing at least 
25% for errors in the determination and in the reduction fac- 
tor. Normal pats in air and water are made for soundness tests. 

Interpretation of Results. — The strength and the normal pat 
tests are practically the only criteria of the quality of natural 
cements, since the fineness of the material has little efifect on 
its soundness or permanency. The fact that unsoundness or 
failure in strength develops as a rule much earlier in naturals 
than in Portlands much simplifies the interpretation of results. 
In general, a natural cement that is sound in the normal j^jats. 
passes the given minimum strength requirements, and devel- 
ops an increase in strength of over 20%, between 7 and 28 days, 
will be found entirely satisfactory in use. ¥ov avoiding diffi- 
culties and delays in construction it is well lor it to jkiss the 
given requirement for setting, although failure in this test, as 
a rule, but little afTects the structural value of the material. 

IMPROVED CEMENTS. 

Improved cements are of the mixed or l)len(led class, and are 
made by grinding together natural cement niixeii with from 
10 to 30 i)er cent, of Portland clinker. 



264 



PRACTICAL CEMENT TESTING. 



The methods of testing and the interpretation of resuhs are 
similar to those employed for naturals, the chief differences 
between improved and natural cements being the greater 
strength, the slightly slower set, and the heavier specific gravity. 
The average results of tests on many samples of improved ce- 
ments made in the author's laboratory are shown in Fig. 137. 
The strength specification requirements for improved cements 
should be increased to 200 and 300 pounds for 7 and 28 days 
neat, and to 120 and 200 pounds, for i :2 mortar at the same 
periods. Ottawa sand mortar should give 145 and 240 pounds. 

The advantages of this material are first a more uniform 
product, on account of the controlling action of the Portland 
cement, and secondly a much increased strength, which in- 
creases more rapidly than the content of Portland cerxient, or 



500 



-F^400 



SS"50o 

'^g.EOO 



100 




^s 



50O 

4oa 

300 
200 
100 



1 7 28 J 2 .3^ 4 6 8 10 \Z 

H-Days-->H - Months - >\ 

Fig. 137 —The Strength of Improved Cements. (From Tests by the Author.) 

the proportionate increase in cost. Results of tests of mixtures 
of Portland and natural cements are shown in Table LV. Im- 
proved cements are especially adapted for masonry and brick 
work, on account of the fat, rich mortar formed, and the greater 
strength developed, as compared w4th those of natural cement. 

'POZZUOLANA CEMENTS. 

Pozzuolana cements (also spelled puzzolana and puzzolan) 
are hydraulic cements, made by grinding a pozzuolanic mate- 
rial, such as blast furnace slag or volcanic scoria, with dry 
slaked lime. , 

A number of natural pozzuolanic materials are employed in 
Europe for this class of cement, but none have been found in 
this country. This w^as the type of cement used by the old 
Romans in their extensive hydraulic constructions, the pozzuo- 
lana being of volcanic origin found near the foot of Mt. Vesu- 



XATi'RAL, SLAG AXD OTHER CBMEXTS. 265 

vius at a place called Pozzuoli, from which the material ob- 
tained its name. A similar material of volcanic origin known 
as trass occurs in German) and Holland, and is employed for 
the same purpose. 

Arenes, a quartzose sand mixed with clay, is another type of 
pozzuolana found in France. The greater part, however, of 
pozzuolanic cements, at the present time, are made from an 
artificial material resulting from the quenching or granulation 
of blast furnace slag, and since this is the only form of this ma- 
terial made in this country, the others will not be considered 
further. 

SLAG CEMENTS. 

Although cement made from a mixture of lime and granu- 
lated blast furnace slag has been used in Europe over 20 years, 

TABLE LV. — Tensile Strength of Mortars made with Mixtures of Natural 

and Portland Cement. 

(From Sabin's ".Cement and Concrete.") 



Number vl^^^^L^ Per I Portland 

Biiquettes Cent \ Natural 



1 7 days 

2 28 days 

3 . . 6 months 

4 I year 

5 2 years 

6 3 years 



100 ' 


50 




12.5 








50 


75 


87.5 


100 


291 


205 


108 


75 


24 


357 


264 


219 


190 


123 


550 


425 


Zl^ 


300 


322 


574 


441 


3to 


}>i(^ 


291 


543 


449 


375 


343 


Z^i 


592 


501 


428 


370 


429 



Mixture— 1 cement : 2 "Point aux Pins" saud, passing No. 10 sieve. 
Each result mean of 10 tests. 



it was not until 1896 that a patent was granted to Mr. Jasper 
Whiting, of the Illinois Steel Company, for the production of 
this material in America. That year, this company maile over 
12,000 barrels of slag cement, while in 1903, the production 
amounted to 525,8(/) l)arrels, made at seven plants. tw(^ in .\la- 
bama, and one each in Illinois, Maryland, \ew Jerscx. ( )hio 
and Pennsylvania. 

Composition. — The method em])l()ye(l in preparing the slag 
for this cement is to plunge it when still in a molten state into 
water, which not only makes it granular, but also prevents the 
breaking down of the complex compounds into the simple «Hies 
which form on cooling, thus retaining its structure and giving 
to it pozzuolanic proi)crtits. Slag allowed to cool slowly jx^s- 



266 PRACTICAL CEMENT TESTIXG. 

sesses scarceh any of these properties and is unfit for cement. 
Another great advantage of this granulation is the driving off 
of the excess of sulphur in the form of hydrogen sulphide gas. 

The slags employed for this material must be basic, and low 
in magnesia and sulphur. Prof. Tetmajer states* that slags in 
which the ratio of lime to silica is unity are not suitable, but 
that above this proportion their value increases with this 
ratio. He also states that the best results are obtained from 
slags having a ratio of alumina to silica of between 0.45 and 
0.50, the best ratio for the ingredients being — silica : alumina : 
lime = 30 : 16 : 46. 

According to M. Prostf the slags used generally for the mak- 
ing of cements may be very nearly represented by the 
formula 2 SiO^, AUO3, 3 CaO, while slags of the formula 2 
Si02, AL,03, 4 CaO, may be used if quenched rapidh. He also 
states that a considerable proportion of sulphur may be pres- 
ent and not deleterious to the cement, although this is opposed 
to the consensus of opinion. 

The specifications employed by the Illinois Steel Company 
for slags suitable for cement are : 

"Silica plus alumina, not over 49 per cent. 
Alumina — 13 to 16 per cent. 
Magnesia — not over 4 per cent. 

''Slag must be made in a hot furnace, and must be of a light 
gray color. 

"Slag must be thoroughly disintegrated by the action of a 
large stream of cold water directed against it with consider- 
able force. This contact should be made as near the furnace as 
is possible." 

The sulphur content is commonly restricted to 1.25 per cent. 
The amount of slaked lime to be added depends upon the com- 
position of the slag and may vary from 5 to 30 per cent, of the 
finished product. It is customary in many plants to add a small 
proportion of caustic soda, from i to 3 per cent., for the pur- 
pose of accelerating the set, the soda being usually dissolved in 
the water in which the lime is slaked, and thus added to the 
material. Analyses of several slags, and the cements made 
from them are shown in Table LVI. 



^Annales de les Construction, July, 1886. 
■;Aunaies aes Mines, i6oy. 



NATURAL, SLAG AND OTHER CEMENTS. 



267 



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tuo 


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-iri 


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268 PRACTICAL CEMENT TESTING. 

Manufacture. — The following description of the manufacture 
of slag- cement is taken from a statement* of the process made 
bv Jasper Whiting, of the Illinois Steel Company, and is typical 
of the customary methods : 

"Slag of the proper composition is made to flow from the 
furnace in which it is produced through an open trough to the 
chilling tank, where a large stream of cold water under high 
pressure is directed against it at right angles to its flow. Con- 
tact between the slag and cold water not only causes the slag 
to break up and disintegrate, but eliminates about one-third of 
its sulphur and changes it chemically in such a way as to render 
it suitable for the manufacture of cement. 

"After each lot of slag is chilled a sample of it is taken and 
examined both chemically and physically in the laboratory. 
If the results of this examination are, satisfactory, an- 
other sample is taken and mixed with a definite proportion 
of prepared lime and the whole ground in a miniature mill where 
actual cement is produced, which is also submitted to physical 
and chemical tests. 

"The preliminary examination of the raw materials being 
complete, the slag is then passed through a dryer and conveyed 
by an elevator into bins located over grinding mills of the 
Griffin type, which are used for preliminary pulverization. It 
is then conveyed by means of another elevator into bins over 
grinding machines of the tube-mill type, where it is mixed with 
the proper proportions of prepared lime, as previously deter- 
mined, and the two materials ground and intimately mixed to- 
gether in the above mentioned tube-mills. The resulting pow- 
der, w^hich is so fine that not over 4 per cent, is left on a 200- 
mesh sieve, is conveyed by means of screws and elevators into 
large bins, from which it is drawn and packed into barrels and 
bags for the market. 

"An important element in the manufacture of cement is the 
prepared lime. This lime, obtained from the calcination of 
limestone, is unloaded into bins beneath which are placed two 
screens of different mesh, the coarse at the top. A quantity of 
lime is drawn on the top screen, where it is slaked by means 
of the addition of water containing in solution a small percentage 

*Peport of Board of Engineers U. S. A. on Steel Portland Cement, 1900, Ap- 
pendix L. 



NATURAL, SLAG AXD OTHER CEMENTS. 269 

of caustic soda. As the material is slaked it falls through the 
coarse screen on to the finer screen, after passing which it falls 
into a conveyor and is conveyed to a rotary dryer. It would be 
perfectly possible to slake this lime and incorporate with it the 
desired Cjuantity of caustic soda without any additional heat, 
but by so doing there is great danger of having present particles 
of unslaked lime, which would render the resulting cement unfit 
for use. The wet and perfectly slaked lime , therefore, is con- 
veyed into the aforementioned dryer, and the final slaking done 
by the application of heat, so that every particle of lime is 
thoroughly slaked and the soda incorporated with it in the most 
perfect manner. The resulting prepared lime is then conveyed 
by means of elevators and screws into hoppers over the tube 
mills, where it is mixed with the ground slag in known but vary- 
ing proportions." 

Color and Weight. — Slag cement may usually be recognized by 
its bluish color and its very light weight, neither of which 
characteristics, however, may be considered as criteria of quality. 
The cement is packed in bags or barrels, which should weigh 
not less than 82^ and 330 pounds respectively, four of the bags 
equalling a barrel. 

Specific Gravity. — Since the ingredients of this material are 
not burned together, the specific gravity of the cements equals 
the sum of the specific gravities of the ingredients (2.0 to 2.^ 
and 2.8 to 3.0), thus averaging from 2.6 to 2.85. Some speci- 
fications require a specific gravity of not less than 2.j, while 
others place both a maximum and minimum limit of. say, be- 
tween 2.7 and 2.8, although the results of this test give but little 
indication of the constructive value of the material. The results 
tend to decrease with the age of the cement, due to the absorp- 
tion of carbonic acid by the lime. 

Fineness. — To produce a proper reaction on the adilition of 
mixing water, it is nQ,cessary that slag cements ho ground to a 
much greater degree of fineness than is necessary with Port- 
lands, thus rendering them more susceptible to exterior con- 
ditions, some of which are beneficial while others are deletonous. 
Conmion practice is to re(|uire not less than i)/% to pass the 
No. 100, and from 90 to 92^0 to pass the No. 200 sieve. 

Time of Setting. — Most slag cements, made of a sinii)le mix- 



270 PRACTICAL CEMENT TESTING. 

ture of lime and slag, set so very slowly that they are difficult 
to use in practice, and hence it is customary to add a small per- 
centage of caustic soda to the water in which the lime is slaked, 
thus increasing the rate of setting. If stored for a long time, 
however, the soda becomes carbonized and its effect disappears, 
the cement thus becoming slower setting with age. The speci- 
fication requirements are generally similar to those for Portland 
cements, but it is especially important that the hard set require- 
ment (usually 10 hours) be fulfilled with this material. 

In spite of the fine grinding of slag cements, the amount of 
water required to bring them to normal consistency will average 
about 18% or 2 to 3% less than Portlands; otherwise the con- 
duct of the test is similar. 

Tensile Strength. — The strength of slag cements is tested in 
briquettes, both of neat paste and of sand mortar, made usually 
in the proportion of one part of cement to three parts of sand. 
Owing to the extreme fine grinding, the neat results are apt to 
be low, with the sand abnormally high, occasionally even equal- 
ling the neat. The tendency of the material prior to test is to- de- 
crease in strength with age, owing to the carbonization of the 
lime, while most other exterior conditions operate in a manner 
similar to Portland cements. In general, the results of the sand 
tests equal those of Portland cements, while the neat values are 
lower. The specifications'^' of the U. S. Army require 350 and 
500 pounds neat, and 140 and 220 pounds with i : 3 mortar at 
the end of 7 and 28 days respectively. The reportf accompany- 
ing these specifications states: "Mortars and concretes made 
from Puzzolan approximate in tensile strength similar mixtures 
of Portland cement, but their resistance to crushing is less, the 
ratio of crushing to tensile strength being about 6 or 7 to i for 
Puzzolan, and 9 to 11 to I for Portland." 

Soundness. — The most important elements that may operate 
to produce unsoundness in slag cements are unslaked lime and 
excess of sulphides or magnesia. If the lime is not sufficiently 
slaked, or is coarsely ground, it will tend to produce swelling 
and disintegration, as with Portlands. The effect of sulphur in 
the form of sulphides is noticeable chiefly in air, where they 
oxidize to sulphates with a great change in volume, thus causing 

*9ee Appendix D. 

fProfessional papers No. 28, Coip.'^ of Engineers, U. S. A. 



NATURAL, SLAG AND OTHER CEMENTS. 



2yi 



disintegration ; in water this change does not occur, although 
the pats generally show blotches of a bluish or greenish gray, 
due probably to the formation of iron sulphide. 

The tests are made on normal pats and on specimens sub- 
mitted to boiling, and should at the end of 28 da} s give, in the 
normal pats, no indication of unsoundness other than blotching, 
and should also pass the boiling test. Failure in either case 
should mean rejection. 

Chemical Analysis. — Analysis of the essential ingredients gives 
little or no indication of the quality of slag cements. An excess 
of magnesia or of sulphur in the form of sulphides may produce 
unsoundness, and hence these ingredients should be limited to 
4 and 1.3 per cent, respectively. 

Testing of Slag Cements. — The methods of testing slag cements 
are practically identical with those for Portlands, the only notice- 
able difiference being the smaller amount of water required to 
produce normal consistency. The methods of approximate 
testing given in Chapter XIII. are also entirely applicable to 
this material. 

The essential tests are those of strength and soundness. Of 
lesser importance are fineness and time of setting, while that of 
specific gravity is of almost no value. It is advisable that the 
amount of sulphide sulphur always be determined if possible 
and never allowed to exceed 1.3 per cent. The specifications of 
the U. S. Army Engineers for this material are given in Ap- 
pendix D. 

Adaptability. — Slag cements are well suited for constructions 
in sea-water or in heavy foundations or other constructions 
such as sewers, conduits or other underground work, where con- 
stantly exposed to moisture. They, however, are not suited 
for an}/ construction much exposed to the air, for under sucli 
conditions they are liable to disintegrate by reason of the oxida- 
tion of the sulphides, nor for work subject to either wearing or 
shocks, even when subjected to moisture. T\w wliite elTK^r- 
escence usually appearing on the surface of slag cement con- 
cretes is an additional reason for not using this material where 
the appearance of the structure might thus be marred. 



2^2 



PRACTICAL CEMENT TESTING. 



SAND CEMENT. 

' This material is produced by the fine grinding of an intimate 
mixture of sand and Portland cement, usually in equal propor- 
tions, although mixtures as lean as i cement to 6 sand have been 
made to compete with low grade natural cements. The sand 
should be clean and silicious, while the degree of fineness of the 
finished material must be such that at least 95 per cent, shall 
pass the No. 200 sieve. 

Although neat briquettes of this cement are weaker than the 
Portland cement from which it is made, briquettes of i : 3 sand 
mortar give almost equal strength, dueto the extreme fineness 
of the cement, which enables it to form a more perfect coating 
on the sand grains, and also to the fine particles of sand, which 
produce a better graded and hence denser mortar. The fine 
grinding of the cement also is beneficial in furthering the season- 
ing of any expansives that may be present. 

The cement should be tested for strength (with sand only), 
soundness and time of setting, and should pass the specifications 
for Portland cement. The fineness should be such that 95% 
should pass the No. 200 sieve. A few tests made on sand 
cements of dififerent proportions are shown in Table LVII. This 
cement is a patented article, but may be made by anyone on pay- 
ment of a royalty. Mr. Sabin states'^' that "in the construction 
of Lock and Dam No. 2, Mississippi River, this process was 
used, grinding with a tube mill one part of Portland cement 
with one part fine sand. The cost, exclusive of plant, was esti- 
mated as follows : 

-| barrel of Portland cement at $2.85 $1.42 

•J barrel of sand at $0.05 03 

Cost of grinding 50 

Cost of ro\alty 05 

Cost of one barrel sand-cement $2.00" 

thus effecting a saving of $0.85 cents per barrel less interest and 
depreciation of plant. 

MIXED CEMENTS. 

These are products resulting from the blending of Portland 
cements with raw rock, slag and natural cement, or from other 

*In "Cement and Concrete," by L. C. Sabin. 



NATURAL, SLAG AND OTHER CEMENTS. 



273 



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274 



PRACTICAL CEMENT TESTING. 



artificial mixtures. They are commonly sold either as "second 
grade" Portlands or as natural cements. They exist in so many 
different varieties that it is impossible to consider or discuss 
them as a class. Tests for strength, soundness and time of 
setting should be made on them, the other tests affording but 
little information. Cements of this kind should never be em- 
ployed in high grade construction, but occasionally may be used 
to advantage in rough foundation work, or in other cases where 
the best grades of material are not essential. 



CHAPTER XVI. 

SPECIFICATIONS. 

The requirements for a good cement specification, or indeed 
for the specification of any material, are, first, that it be suf- 
ficiently severe to insure good material without containing re- 
quirements that' unnecessarily hamper the manufacturer; second, 
that it be definite or free from ambiguous clauses, and, third, 
that it be well balanced. 

The clauses of a cement specification should cover require- 
ments for the storage and inspection of the shipments, the con- 
dition and weight of the packages, the method of testing to be 
followed, a definition of the material, the values to be obtained 
in the various tests, and the regulations regarding the accept- 
ance or rejection of the shipments. The tests to which a cement 
should be subjected are specific gravity, fineness, time of setting, 
tensile strength neat and with sand, soundness, and the chemical 
determination of certain ingredients. 

Although in the past there have been frequent examples of 
specifications of unnecessary severity, such caces are much less 
common than heretofore, thanks to the work of various tech- 
nical societies in formulating standard specifications, and in 
bringing before the public, information regarding the values 
which should be obtained on a normal cement from each of 
these tests. Probabl}/ the most popular fallacy regarding the 
testing of cement is that great strength necessarily implies in- 
creased structural valiie, and hence there is a tendency on the 
part of certain engineers who have not taken the trouble to in- 
vestigate the subject, to increase the requirements for tensile 
strength, with the purpose of securing an especially fine rrade oi 
material, when in fact the material furnished under such speci- 
fications is generally over-limed and i)lastered and, while giving 
high short time tests, will ultimately be inferior to the lower 
testing material, and also is much more susceptible to influences 
causing disintegration. Too low a re{|uirement, on the other 
hand, will permit the use of an inferior or adulterated product. 



276 PRACTICAL CEMENT TESTING. 

which in service may be insufficient to meet the demands re- 
quired of the structure. 

The same principle appUes to all the other tests to which 
the cement may be subjected, an abnormally high specification 
requiring a forced product liable to give unsatisfactorv service, 
and a low one permitting the use of inferior material, so that it 
is only by a most careful study of the available data that an 
original specification can be drafted that will ensure the furnish- 
ing of the best material. 

While, as has been stated, the average qualities which a nor- 
mal cement must possess are becoming much better understood, 
there is nevertheless in many recent specifications a lack of 
definiteness which is often sufficient to almost entirely destroy 
their value. First and foremost is the common omission of any 
clause or reference indicating the method to be employed in 
m.aking the various tests. It has been shown in the previous 
chapters of this book what a great influence the methods and 
appliances used have upon the final results, and yet the majority 
of specifications require in, say, tensile strength, that the ma- 
terial shall develop a neat strength of, say, 500 pounds, at 7 days 
without any further qualifications, although it may easily be pos- 
sible to obtain results of from- 300 to 800 pounds according to 
the manner in which the material is treated. Although the 
method followed exerts probably a greater influence on tensile 
strength than on the other determinations, it nevertheless does 
apply to all of them, although in varying amounts, so that prac- 
tically, unless a definite method of testing be stipulated, the 
acceptance of the material depends actually more upon the 
quality of the tester than on that of the cement itself. 

For the average consumer, especially one just organizing a 
laboratory for the first time, it is best to stipulate in the specifica- 
tions that the methods to be followed shall be in accordance 
with one of the standard methods, preferably that of the Com- 
mittee of the American Society of Civil Engineers. In one 
particular, however, that of standard sand, the recommendations 
of this Committee are followed but rarely, so that it will generally 
be necessary to qualify the method in that detail if any other 
sand is to be used. The steaming test, moreover, has been 
found by all those who have investigated it in other than a 
superficial manner to be inferior to the boiling test in the re- 



SPECIFICATIONS. 



277 



liability of its indications. Most consumers, therefore, should 
alter the method in these two particulars, but otherwise follow 
it implicitly in the conduct of the various tests. A clause to the 
following effect, therefore, will at once place the specification on 
a definite and standard basis, and will to a great extent preclude 
the rejection of good material, or the acceptance of bad material 
by reason of irregularities in the making of the determinations : 

''All tests shall be made in accordance with the methods 
prescribed by the Committee on Uniform Tests of Cement of 
the American Society of Civil Engineers, reported January 21, 
1903, and amended January 20, 1904, except in the following 
two particulars : 

*'(i) Sand of crushed quartz shall be substituted for Ottawa 
sand, the standard size remaining the same. 

''(2) For the 'steam' test shall be substituted the boiling test, 
hereinafter described." 

An even better method to be followed in drafting specifications 
for which the tests will be made in an established, well-equipped 
laboratory, is to stipulate that ''all tests shall be made in ac- 
cordance with the standard methods of testing now on file in 
the office of the Chief Engineer," these methods containing an 
exact description of every appliance and detail of the processes 
employed. The reason for this is that a well-organized labor- 
atory will discover many small variations from the standard 
method that will much facilitate the routine of testing without 
in any way affecting the results to an appreciable extent. Now, 
if the standard method is specified and any of these variations is 
employed, the whole series of tests may be discredited and with 
reason, whereas if the laboratory has a record of its standard 
method which is specified and followed in practice, no such ques- 
tio«i can be raised. It is advised, however, that except for the 
use of the sand and the form of accelerated test reconnncnded, 
that the methods specified conform as closely as possible to the 
report of the Committee, and thus arrive at as nearly standard 
methods as can be. 

If no such method be stipulated, the specifications must con- 
tain complete information as to the essential points in the con- 
duct of the tests, especially the normal consistency employed, 
the method of making and haiulHng bri(|uettes and pats, and 



278 PRACTICAL CEMENT TESTING'. 

descriptions of the apparatus, for unless this is done any speci- 
fication, no matter how well drawn, is almost valueless. 

Lack of definiteness in two other clauses also is often the 
cause of much annoyance — that relating to the facilities to be 
provided for inspection and testing, and that assigning the power 
of rejection to a certain individual. These provisions should be 
especially clear to prevent misunderstanding or friction. 

The foregoing criticisms, it must be acknowledged, aooly 
rather more to specifications of the past than the present since 
the wide publicity given in recent years to this subject has done 
much to promote greater familiarity with the essentials for good 
specifications. One fault, however, that still exists in many 
specifications is a lack of balance between the various require- 
ments, which is apt to call for material almost impossible to 
produce, or to destroy the value of the other requirements. As 
a rule, specifications of this character show indications of having 
been drafted with a pair of shears, by an engineer who fully un- 
derstood the purpose of the various requirements, but was un- 
familiar with their inter-relations. 

For example, a specification recently issued by the engineer 
of a city in the middle-west called for a slow^-setting Portland 
cement, one finer than usual, and at the same time limited to 
content of sulphuric acid 1%, which would be a material prac- 
tically impossible for most mills to produce. The engineer un- 
doubtedly understood that a fine, slow setting cement was 
superior, and knew that high sulphuric acid might be deleterious, 
and having seen a specification, possibly of the French Govern- 
ment, limiting this element to 1%, he combined the three re- 
quirements, intending to secure an especially fine grade of ma- 
terial, but in reality precluding the use of some of the best 
cements. As it also happened the nature of the work was such 
that even an abnormal amount of sulphuric acid would not have 
affected its structural value. 

Another "cribbed" clause often found is one limiting the con- 
tent of magnesia in Portland cements to 2%, which may be 
met by certain brands, but which at one stroke practically elimi- 
nates all the excellent cements of the Lehigh Valley District, 
and at the same time does not secure better material. Another 
instance of lack of balance is frequently found in the fineness 
requirements, the author having had brought to his notice speci- 



SPECIFICATIONS. 279 

fications for Portland cement, one calling for a residue of less 
than 15% on the No. 100 and 25% on the No. 200 sieve, and the 
other 8% on the No. 100 and 30% on the No. 200, the No. 100 
requirement in the first case and the No. 200 in the second being 
almost worthless. The same lack of balance often occurs be- 
tween the specifications for setting and fineness, fineness and 
strength, strength neat and strength with sand, etc., thus 
destroying much of their value. An engineer, unless well posted 
in the properties of cement, should therefore never attempt to 
combine the clauses from several specifications into one, but 
should either adopt one in its entirety or drop it altogether. 

The recently published and most excellent standard specifica- 
tions'^ issued by American, English and Canadian societies and 
also by such bodies as the Corps of Engineers of the U. S. Army 
have done much to better this condition. Considered only in 
the light of a clear, consistent and well-balanced specification, 
that of the Corps of Army Engineers ranks easily first, although 
the methods of testing employed are often unscientific in char- 
acter and leave much to be desired. Those of the Committee 
of the American Society of Testing Materials are generally ex- 
cellent, but are defective in the indefiniteness of the strength 
requirements, and also in the extremely low minimum values 
recommended, especially when it is considered that Ottawa sand 
and not crushed quartz is used. 

Although it may be considered unwise to propose another 
specification, in view of the existence of these standards, it 
nevertheless cannot be denied that neither of these specifications 
is adapted to use exactly as it stands, the methods of testing in 
one instance, and the poor strength re(|uirenients in the other, 
leaving much to the discretion of the engineer, whose experience 
in these lines may not have been sufficient to j^roperly make 
the necessary corrections. The following, therefore, is given 
as a cement specifica-tion which max be incori^orated directly 
into the general specifications for construction work, and which, 
while insuring the furnishing of first-class material, will at the 
same time require only a normal product which any reputable 
manufacturer would be entirely willing to furnish, and nhirecner 
will not limit competition to any class of cements, nor to those 
produced by any particular process or in an\ special locality. 

See Appendices. 



28o PRACTICAL CEMEXT TESTIXG. 

SPECIFICATIONS FOR PORTLAND CEMENT.* 

1. Definition. — The cement shall be Portland cement of the 
best quality, dry and free from lumps. By Portland cement is 
meant the finely pulverized product resulting from the calcina- 
tion to incipient fusion of an intimate mixture of properly pro- 
portioned argillaceous and calcareous materials, and to which 
no addition greater than 3% has been made subsequent to cal- 
cination. 

2. Inspection. — All cements shall be inspected, and those re- 
jected shall be immediately removed by the contractor. Every 
facility shall be provided by the contractor and a period of a: 
least twelve days allowed for the inspection and necessar\ tests. 
Cement faiHng to meet the seven day requirements 'may be held 
awaiting the results of the twenty-eight day tests before rejec- 
tion. 

3. Storage. — While awaiiing the results of the tests, the ce- 
ment shall be stored in a suitable weather-tight building, having 
the floor properly blocked or raised from the ground, and shall 
be so stored as to permit easy access for the proper inspection 
and identification of each shipment. 

4. Packages. — Cement shall be packed in strong cloth or can- 
vas sacks, or in sound barrels lined with paper, which shall be 
plainly marked with the brand and the name of the manufac- 
turer. t 

5. Weight. — A barrel of cement sh:ill contain 4 bags and shall 
weigh not less than 376 pounds net. A bag shall contain not 
less than 94 pounds net of cement. The weights of the separate 
packages shall be uniform. 

6. Tests. t — All tests shall be made in accordance with the 
methods prescribed by the Committee on Uniform Tests of Ce- 
ment of the American Society of Civil Engineers, reported 
January 21, 1903, and amended January 20, 1904. except in the 
following two particulars : 

(i) Sand of artificially prepared crushed quartz of the 
same size shall be substituted for Ottawa sand. 



♦These specifications are taken largely from the variou? standard specifi- 
cations, as well as those of municipalities, and important engineering constructions. 

^If the specifications are for the direct purchase of cement, there should be 
added to this clause: — "Packages received in broken or damaged condition may 
be rejected or accepted zlb fractional packages." 

iOr the following clause mav be substituted for (6"> : — "All tests shall be made 
in accordance with the standard methods now on file in the office of the Chief 
Engineer, copies of which may be had on application." 



SPECIFICATIONS. 281 

(2) The boiling test, hereinafter described, shall be sub- 
stituted for the "steam" test. 

7. Acceptance. — The acceptance or rejection of a cement shall 
rest with the Chief Engineer, and shall be based upon the follow- 
ing requirements : 

8. Specific Gravity. — The specific gravity of the cement shall 
be not less than 3.10. 

9. Fineness. — It shall leave a residue of not more than 8% by- 
weight on the No. 100, and not more than 25% on the No. 200 
sieve. 

10. Time of Setting. — It shall develop initial set in not less 
than 20 minutes, and must develop hard set within 10 hours. 

11. Tensile Strength. — Briquettes one inch square in cross sec- 
tion shall develop not less than the following tensile strengths 
and shall show no retrogression in strength within the periods 
specified : 

NEAT CEMENT. 
Age. Strength. 

24 hours (in moist air) 175 lbs. 

7 days (i day in moist air, 6 days in water) 500 

28 days (i day in moist air, 27 days in water) 600 

ONE PART CEMENT, THREE PARTS STANDARD 

SAND. 

7 days (i day in moist air, 6 days in water) 170 lbs. 

28 days (i day in moist air, 27 days in water) 240 "* 

12. Soundness. — Two pats of neat cement c^f n(M-mal consist- 
ency about 3 ins. in diameter, one-half inch thick at the center 
and tapering to thin edges, and a ball of the same material about 
i:|: ins. in diameter, shall be kept in moist air for a period of 24 
hours. 

(a) A pat is then kept in air at normal tcmperatifro. and 
observed at intervals for at least 28 days. 

(b) A pat is kept in water maintained as near yo^ I'^ahr. 
as practicable, and observed at intervals for at least 28 
days. 

•Additional security may be attained by specifying a maximum iioat strength 
of Sr)() lbs. at seven days, and also an increase in the sand strength bv^tween 
the two periods of not loss than 10'". Kxccpt for constructions of unusual im- 
portance, liowever, tliis clause is not rccDniinriulcl. 



282 PRACTICAL CEMENT TESTING. 

(c) The ball is placed in water at normal temperature, 
which is gradually (in about half an hour) raised to boiling 
and maintained there for 3 hours. 
The pats, to pass the requirements satisfactorily, shall remain 
firm and hard and show no signs of distortion, blotching, check- 
ing, cracking or disintegration. The ball when removed from 
the water shall show no signs of checking, cracking, or disin- 
tegration. 

13. Chemical Requirements. — The cement shall not contain 
more than 1.75% of anhydrous sulphuric acid (SO3), nor more 
than 4% of magnesia (MgO). 

SPECIFICATIONS FOR NATURAL CEMENT. 

1. Definition. — The cement shall be natural cement of the best 
quality, dry and free from lumps. By natural cement is meant 
the finely pulverized product resulting from the calcination of an 
argillaceous limestone at a temperature below that necessary to 
cause incipient fusion. 

2. Inspection. — All cements shall be inspected, and those re- 
jected shall be removed immediately by the contractor. Every 
facility shall be provided by the contractor and a period of at 
least twelve days allowed for the inspection and necessary tests. 
Cement failing to meet the seven day requirements may be held 
awaiting the results of the twenty-eight day tests before rejec- 
tion. 

3. Storage. — While awaiting the results of the tests, the cement 
shall be stored in a suitable v/eather-tight building, having the 
floor properly blocked or raised from the ground, and shall be 
so stored as to permit easy access for the proper inspection and 
identification of each shipment. 

4. Packages. — Cement shall be packed in strong cloth or can- 
vas sacks, or in sound barrels lined with paper, which shall be 
plainly marked with the brand and the name of the manufac- 
turer.* 

5. Weight. — A barrel of cement shall contain 3 bags and shall 
weigh not less than 282 pounds net. A bag shall contain not 
less than 94 pounds net of cement. The weights of the separate 
packages shall be uniform. 

*See foot note to clause (4)— Portland Cement, page 280. 



SPECIFICATIONS. 283 

6. Tests.* — All tests shall be made in accordance with the 
methods prescribed by the Committee on Uniform Tests of Ce- 
ment of the American Society of Civil Engineers, reported 
January 21, 1903, and amended January 20, 1904, except that 
sand of artificially prepared crushed quartz of the same size shall 
be substituted for Ottawa sand. 

7. Acceptance. — The acceptance or rejection of a cement shall 
rest with the Chief Engineer, and shall be based upon the fol- 
lowing requirements : 

8. Specific Gravity. — The specific gravity of the cement shall 
not be less than 2.80. 

9. Fineness. — It shall leave a residue of not more than 15% by 
weight on the No. 100, and not more than 30% on the Xo. 200 
sieve. 

10. Time of Setting. — It shall develop initial set in not less than 
10 minutes, and hard set in not more than 5 hours. 

11. Tensile Strength. — Briquettes one inch square in cross sec- 
tion shall develop not less than the following tensile strengths 
and shall show no retrogression in strength within the periods 
specified. 

NEAT CEMENT. 
Age. Strength. 

24 hours (in moist air) : . 40 lbs. 

7 days (i day in moist air, 6 days in water) 125 *' 

28 days (i day in moist air, 2^ days in water) 225 '* 

ONE PART CEMENT, TWO PARTS STANDARD SAXD. 

7 days (i day in moist air, 6 days in water) y^ lbs. 

28 days (i day in moist air, 27 days in water) 140 

12. Soundness. — Two pats of neat cement of normal consist- 
ency about 3 ins. in diameter, l-\\\. thick at the center and lai)cr 
ing to thin edges shall be kej)t in moist air for a period of 24 
hours. 

(a) A pat is then kept in air at normal temperature. 
(1)) The other pat is ke])t in water maintained as near yo' 
Eahr. as practicable. 

These pats shall be obs-erved at intervals for at least j8 days. 
and to satisfactorily pass the re(|uircmcnts shall remain firm and 

♦See foot nolo (o chiuso ((!)— Portland (\nnoiit. ])am' '-'SO. 



284 PRACTICAL C EM EXT TESTIXG. 

hard, and show no signs of distortion, checking, cracking or dis- 
integration. 

INTERPRETATION OF SPECIFICATIONS. 

In the interpretation of the results of specification tests, it 
must always be borne in mind that the cement should be judged 
from the results of all the tests collectively, and not from the in- 
dividual values. It can be stated that only failure in the normal 
pat tests, or abnormally low values in the sand strength, is 
sufficient to warrant the rejection of the shipment, without other 
evidences of poor quality. For example, let us consider the 
ten Portland cements in Table L^'IIL, all of which occurred in 
the routine of the author's laboratory, it being assumed that the 
specifications just given formed the basis of the testing. 

Cement i is normal in every particular and one which would 
be entirely safe to accept on the seven day test. The second 
cement fails in specific gravitv. and is slightly below the speci- 
fications in sand strength. The boiling test, however, was good, 
and an examination showed neither underburning nor adul- 
teration, thus indicating that the cement was merely old. as also 
was more or less apparent from its condition. The shipment, 
therefore, was accepted at 7 days, and the 2S day test confirmed 
this decision. 

Cements 3 and 8 both gave evidences of being over-Hmed in 
failure in the boiling test and in the high neat strength at 7 days. 
Both of these shipments were held at 7 days, second boiling 
tests made at 2S days, the first passing and the second failing. 
and as a result the first sample was accepted while the second 
was rejected. At the end of 3 months the normal pats of Xo. 8 
had completely disintegrated, while the others remained nor- 
mal except for a very slight curA'ature. Cement 4 is another ex- 
ample of low sand strength and failure in boiling, which was 
accepted on the 28 day test. 

Cements 5 and 6 are both coarse and fail to boil. At 28 days 
Xo. 5 boiled and X'^o. 6 failed a second time. Xo. 5 was ac- 
cepted, therefore, vrhile Xo. 6 was rejected, but at the same 
time the manufacturer who furnished cement Xo. 5 was notified 
that the shipment was coarse, and that future shipments would 
be condemned if this were not rectified. 

Cement 7 is extremely quick setting, and for miost classes of 
construction should be rejected outright. X'o. 9 illustrates a 



SPECIFICATIOXS. 



285 



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236 PRACTICAL CEMENT TESTING. 

thoroughly bad cement, both iinderburned and coarse, while lO 
shows a typical case of adulteration with slag, indicated bv the 
low^ specific gravity, the blotching of the normal pats, as well as 
by the special tests for adulteration. 

The point, however, which it is especially desired to emphasize 
is that while cements 2, 3, 4 and 5 all fail in some particular to 
pass the requirements of the specifications, all of them were 
accepted and proved satisfactory in service. To attempt to hold 
every shipment to pass an absolutely perfect test is not onlv un- 
warranted by experience, but often defeats its own purpose in 
rejecting excellent material, while it also creates much unneces- 
sarv annoyance and delay. 



APPENDIX A. 



Standard Method of Cement Testing. 

Progress Report of the Committee of the American Society of Civil 
Engineers on Uniform Tests of Cement, presented January 21, 1903, and 
amended January 20, 1904. 

Sampling. 

• 

I. — Selection of Sample. — The selection of the sample for testing is a 
detail that must be left to the discretion of the engineer ; the number and 
the quantity to be taken from each package will depend largely on the im- 
portance of the work, the number of tests to be made and the facilities 
for making them. 

2. — The sample shall be a fair average of the contents of the package; it 
is recommended that, where conditions permit, one barrel in every ten be 
sampled. 

3. — All samples should be passed through a sieve having twenty meshes 
per linear inch in order to break up lumps and remove foreign material ; 
this is also a very effective method for mixing them together in order to 
obtain an average. For determining the characteristics of a shipment of 
cement, the individual samples may be mixed and the average tested ; 
where time will permit, however, it is recommended that they be tested 
separately. 

4. — Method of Sampling. — Cement in barrels should be sampled through 
a hole made in the center of one of the staves, midway between the heads, 
or in the head, by means of an auger or a sampling iron similar to that used 
by sugar inspectors. If in bags, it should be taken from surface to center. 

Chemical Analysis. 

5.— Significance. — Chemical analysis may render valuable service va the 
detection of adulteration of cement with considerable amounts of inert 
material, such as slag or ground limestone. It is, of use. also, in deter- 
mining whether certain constituents, believed to be harmful when in ox- 
cess of a certain percentage, as magnesia and sulphuric anhydride, are 
present in inadmissible proportions. While not recommending a definite 
limit for these impurities, the Committee would suggest that the most 
recent and reliable evidence appears to indicate that, for Portland cement, 
magnesia to the amount of 5 per cent, and sulphuric anhydride to the 
amount of T.75 per cent, may safely be considered harmless. 

6.— The deternnnation of the principal constituents of cement— silica, 
alumina, iron oxide and lime— is not conclusive as an indication of quality. 
Faulty character of cement results more frc(|uen(lv from imperfect prepar- 
ation of the raw material or defective burning than from incorrect pro- 
portions of the constituents. Cement made from verv finely-ground 



288 APPENDICES. 

material, and thoroughly burned, may contain much more lime than the 
amount usually present and still be perfectly sound. On the other hand, 
cements low in lime may, on account of careless preparation of the raw 
material, be of dangerous character. Further, the ash of the fuel used in 
burning may so greatly modify the composition of the product as largely 
to destroy the significance of the results of analysis. 

7. — [Method. — As a method to be followed for the analysis of cement, 
that proposed by the Committee on Uniformity in the Analysis of Ma- 
terials for the Portland Cement Industry, of the New York Section of the 
Society for Chemical Industry, and published in the Journal of the Society 
for January 15, 1902, is recommended. 

Specific Gravity. 

8. — Significance. — The specific gravity of cement is lowered by under- 
burning, adulteration and hydration, but the adulteration must be in con- 
siderable quantity to affect the results appreciably. 

9. — Inasmuch as the differences in specific gravity are usually very 
small, great care must be exercised in making the determination. 

10. — When properly made, this test affords a quick check for under- 
burning or adulteration. 

II. — Apparatus and Method. — The determination of specific gravity is 
most conveniently made with Le Chatelier's apparatus. This consists of 
a flask (D), Fig. i (see Fig. 138), of 120 cu. cm. {y.2>2 cu. ins.) capacity, 
the neck of which is about 20 cm. (7.87 ins.) long; in the middle of this 
neck is a bulb (C), above and below which are two marks (F) and (E) ; 
the volume between these marks is 20 cu. cm. (1.22 cu. ins.). The neck 
has diameter of about 9 mm. (0.35 ins.), and is graduated into tenths 
of cubic centimeters above the mark (F). 

12. — Benzine {62 degrees Baume naphtha), or kerosene free from 
water, should be used in making the determination. 

13. — The specific gravity can be determined in two ways : 

(i) The flask is filled with either of these liquids to the lower mark 
(E), and 64 gr. (2.25 oz.) of powder, previously dried at 100° Cent. 
(212° Fahr.) and cooled to the temperature of the liquid, is gradually 
introduced through the funnel (B) [the stem of which extends into the 
flask to the top of the bulb (C)], until the upper mark (F) is reached. 
The difference in weight between the cement remaining and the original 
quantity (64 gr.) is the weight which has displaced 20 cu. cm. 

14. — (2) The whole quantity of the powder is introduced, and the level 
of the liquid rises to some division of the graduated neck. This reading 
plus 20 cu. cm. is the volume displaced by 64 gr. of the powder. 

15. — The specific gravity is then obtained from the formula: 

Weight of cement 

Specific gravity = — ; ' 

Displaced volume 

16. — The flask, during the operation, is kept immersed in water in a jar 
(A), in order to avoid variations in the temperature of the liquid. The 
results should agree within o.oi. 



APPENDICES, 



289 



17.-A convenient method for cleaning the apparatus is as follows- 
The flask IS inverted over a large vessel, preferably a glass jar, and shaken 
vertically until the liquid starts to flow freelv; it is then held still in a 
vertical position until empty ; the remaining traces of cement can be re- 




FiG. 138— Le Chatelier's Specific Gravitv Apparatus. 

moved in a similar manner by pouring into the flask a small i|uaiititv of 
clean liquid and repeating the operation. 

18. — More accurate detcrniinations may be made with tlio picnometor. 

Fineness. 

IQ- — Significance. — It is generally accepted that the coarser particles 
in cement are practically iiitrt, and it is only the extromelv tine powder 
that possesses adhesive or cementing qualities. The more tinely cement is 
pulverized, all other conditions being the same, the more sand it will carry 
3nd produce a mortar of a given strength. 

20. — The degree of final pulverization wiiioh tlu- cement receives at the 
place of manufacture is ascertained by me isuriug the residue retained on 



290 APPENDICES. 

certain sieves. Those known as the No. loo and No. 200 sieves are rec- 
ommended for this purpose. 

21. — Apparatus. — The sieves should be circular, about 20 cm. (7.87 
ins.) in diameter, 6 cm. (2.36 ins.) high, and provided with a pan 5 cm. 
(1.97 ins.) deep, and a cover. 

22. — The wire cloth should be woven from brass wire having the follow- 
ing diameters : 

No. 100, 0.0045 in. ; No. 200, 0.0024 in. 

2^. — This cloth should be mounted on the frames without distortion ; the 
mesh should be regular in spacing and be within the following limits : 
• No. 100, 96 to 100 meshes to the linear inch. 
No. 200, 188 to 200 meshes to the linear inch. 

24. — Fifty grams (1.76 oz.) or 100 gr. (3.52 oz.) should be used for 
the test, and dried at a temperature of 100° Cent. (212° Fahr.) prior to 
sieving. 

25. — Method. — The Committee, after careful investigation, has reached 
the conclusion that mechanical sieving is not as practicable or efficient as 
hand work, and, therefore, recommends the following method : • f 

26. — The thoroughly dried and coarsely screened sample is weighed and' 
placed on the No. 200 sieve, which, with pan and cover attached, is held 
in one hand in a slightly inclined position, and moved forward and back- 
ward, at the same time striking the side gently with the palm of the other 
hand, at the rate of about 200 strokes per minute. The operation is con- 
tinued until not more than one-tenth of i per cent, passes through after 
one minute of continuous sieving. The residue is weighed, then placed 
on the No. 100 sieve and the operation repeated. The work may be 
expedited by placing in the sieve a small quantity of large shot. The 
results should be reported to the nearest tenfh of I per cent. 

Normal Consistency. 

27. — Significance. — The use of a proper percentage of water in mak- 
ing the pastes* from which pats, tests of setting and briquettes are made, 
is exceedingly important, and affects vitally the results obtained. 

28. — The determination consists in measuring the amount of water re- 
quired to reduce the cement to a given state of plasticity, or to what is 
usur.lly designated the normal consistency. 

29. — Various methods have been proposed for making this determina- 
tion, none of which has beer, found entirely satisfactory. The Committee 
recommends the following: 

30. — Method. Vicat Needle Apparatus. — This consists of a frame 
(K), Fig. 2 (see Fig. 139), bearing a movable rod (L), with a cap (A) 
at one end, and at the other the cylinder (B), i cm. (0.39 in.) in diam- 
eter, the cap, rod and cylinder weighing 300 gr. (10.58 oz.). The rod, 
which can be held in any desired position by a screw (F), carries an in- 
dicator, which m.oves over a scale (graduated to centimeters) attached 
to the frame (K). The paste is held by a conical, hard-rubber ring (I), 

*The term "paste" is used in this report to designatp a rrixture of cement and 
water, and the word "mortar" a mixture of cement, sand and water. 



APPENDICES. 



291 



7 cm. (2.76 ins.) in diameter at the base, 4 cm. (1.57 ins.) high, resting 
on a glass plate (J), about 10 c. m. (3.94 ins.) square. 

31. — In making the determination, the same quantity of cement as will 
be subsequently used for ec.ch batch in making the briquettes (but not 
less than 500 grams) is kneaded into a paste, as described in Paragraph 58, 
and quickly formed into a ball with the hands, completing the operation by 
tossing it six times from one hand tO' the other, maintained 6 ins. apart;: 
the ball is then pressed into the rubber ring, through the larger opening, 
smoothed off, and placed (on its large end) on a glass plate and the 
smaller end smoothed oiff with a trowel ; the paste confined in the ring, 




Fig. 139. — The Vicat Needle. 



resting on the plate, is placed under the rod bearing the cylinder, which 
is brought in contact with the surface and quickly released. 

32. — The paste is of normal consistency when the cylinder i>eiiet rates 
to a point in the mass 10 mm. (0.39 in.) below the toji of the ring. (Ireat 
care must be taken to fill the ring exactly to the top. 

23. — The trial pastes are made with varying percentages of water until 
the correct consistency is obtained. 

34. — The Committee has reconnnended, as normal, a paste, the con- 
sistency of which is rather wet. because it believes that variations in the 
amount of compression to which the bricjuette is subjected in nu>Mlding arc 
likely to be less with such a i)aste. 

35. — Having determined in this manner the proi>er percentage of water 



2()2 APPENDICES. 

required to produce a paste of normal consistency, the proper percentage 
required for the mortars is obtained from an empirical formula. 

36. — The Committee hopes to devise such a formula. The subject proves 
to be a very difficult one, and, although the Committee has given it much 
study, it is not yet prepared to make a definite recommendation. 

Time of Setting. 

Z7- — Significance. — The object of this test is to determine the time 
w^hich elapsed from the moment water is added until the paste ceases to 
be fluid and plastic (called the "initial set"), and also the time required 
for it to acquire a certain degree of hardness (called the "final" or "hard 
set"). The former of these is the more important, since, with the com- 
mencement of setting, the process of crystallization or hardening is said 
to begin. As a disturbance of this process may produce a loss of strength, 
it is desirable to complete the operation of mixing and moulding or in- 
corporating the mortar into the work before the cement begins to set. 

38. — It is usual to measure arbitrarily the beginning and end of the set- 
ting by the penetration of weighted wires of given diameters. 

39. — ^Method. — For this purpose the Vicat Needle, which has already 
been described in Paragraph 30, should be used. 

40. — In making the test, a paste of normal consistency is moulded and 
placed under the rod (L) ; Fig. 2, as described in Paragraph 31 ; this rod, 
bearing the cap (D) at one end and the needle (H), i mm. (0.039 in.) in 
diameter, at the other, weighing 300 gr. (10.58 oz.). The needle is then 
carefully brought in contact with the surface of the paste and quickly 
released. 

41. — The setting is said to have commenced when the needle ceases to 
pass a point 5 mm. (0.20 in.) above the upper surface of the glass plate, 
and is said to have terminated the moment the needle does not sink visibly 
into the mass. 

42. — The test pieces should be stored in moist air during the test; this 
is accomplished by placing them on a rack over water contained in a pan 
and covered with a damp cloth, the cloth to be kept away from them 
by means of a wire screen ; or they may be stored in a moist box or 
closet. 

43- — Care should be taken to keep the needle clean, as the collection of 
cement on the sides of the needle retards the penetration, while cement 
on the point reduces the area and tends to increase the penetration. 

44. — The determination of the time of setting is only approximate, being 
materially affected by the temperature of the mixing water, the tempera- 
ture and humidity of the air during the test, the percentage of water used, 
and the amount of moulding the paste receives. 

Standard Sand. 

45. — The Committee recognizes the grave objections to the standard 
quartz now generally used, especially on account of its high percentage 
of voids, the difficulty of compacting in the moulds, and its lack of uni- 
formity; it has spent much time in investigating the various natural sands 
A\'hich appeared to be available and suitable for use. 



APPENDICES. 293 

46. — For the present, the Committee recommends the natural sand from 
Ottawa, 111., screened to pass a sieve having 20 meshes per linear inch 
and retained on a sieve having 30 meshes per linear inch ; the wires to 
have diameters of 0.0165 and 0.0112 in., respectively, i. e., half the width 
of the opening in each case. Sand having passed the No. 20 sieve shall be 
considered standard when not more than one per cent, passes a No. 30 
sieve after one minute continuous sifting of a 500-gram sample. 

47. — The Sandusky Portland Cement Company, of Sandusky, Ohio, has 
agreed to undertake the preparation of this sand, and to furnish it at a 
price only sufificient to cover the actual cost of preparation. 

Form of Briquette. 

48. — While the form of the briquette recommended by a former Com- 
mittee of the Society is not wholly satisfactory, this Committee is not 
prepared to suggest any change, other than rounding off the corners by 
curves of ^-inch radius. Fig. 3 (see Fig. 43). 

Moulds. 

49. — The moulds should be made of brass, bronze or some equally non- 
corrodible material, having sufficient metal in the sides to prevent spread- 
ing during moulding. 

50. — Gang moulds, which permit moulding a number of briquettes at 
one time, are preferred by many to single moulds ; since the greater 
quantity of mortar that can be mixed tends to produce greater uniformity 
in the results. The type shown in Fig. 4 (see Fig. 46) is recommended. 

51. — The moulds should be wiped with an oily cloth before using. 

Mixing. 

52. — All proportions should be stated by weight ; the quantity of water 
to be used should be stated as a percentage of the dry material. 

53. — The metric system is recommended because of the convenient rela- 
tion of the gram and the cubic centimeter. 

54. — The temperature of the room and the mixing water should he as 
near 21 degrees Cent. (70 degrees Fahr.) as it is practicable to maintain it. 

55.— The sand and cement should be thoroughly mixed dry. The mix- 
ing should be done on some non-absorbing surface, preferably plate glass. 
If the mixing must be done on an absorbing surface it should be thor- 
oughly dampened prior to use. 

56.— The quantity of material to be mixed at one time depends on the 
number of test pieces to be made; about i.ooo gr. (3.S-8 oz.) makes a 
convenient quantity to mix, especially by hand methods. 

57.— The Committee, after investigation of the various nieclianical mix- 
ing machines, has decided not to recommend any machine that has thus 
far been devised, for the following reasons : 

(i) The tendency of most cement is to "ball up" in tin- machine, thereby 
preventing the working of it into a homogeneous paste; (j) there are no 
means of ascertaining wIkmi the mixing is compKte without stopping the 
machine, and (3) the difficulty (»l kei'piu).; thr iniiohim- clean. 



294 APPEXDICES. 

5S. — Method. — The material is weighed and placed on the mixing table, 
and a crater formed in the center, into which the proper percentage of 
clean water is poured; the material on the outer edge is turned into tie 
crater by the aid of a trowel. As soon as the water has been absorbed, 
which should not require more than one minute, the operation is com- 
pleted by vigorously kneading with the hands for an additional 1^4 min- 
utes, the process being similar to that used in kneading dough. A sand- 
glass aflFords a convenient guide for the time of kneading. During the- 
operction of mixing the hands should be protected by gloves, preferably 
of rubber. 

Moulding. 

59. — Hi : .: .:r' :r mortar to the proper consistency, it 

IS at : ::r :r: l :y hand. 

': — - 7 J ^^.s occn unable to secure satisfactory- results with 

T:.r :rr~rr: :. _ machines ; the operation of machine moulding is 

A-er\- slow, and the present t3rpes permit of moulding but one briquette at 
a time, and are not practicable with the pastes or mortars herein recom- 
mended. 

61. — Method. — The moulds should be niled at once, the material pressed 
in firmly with the fingers and smoothed off with a trowel without ram- 
ming; the material should be heaped up on the upper surface of the 
mould, and, in smoothing off, the trowel should be drawn over the mould 
in such a manner as to exert a moderate pressure on the excess material. 
The mould should be turned over and the operation repeated. 

62. — A check upon the uniformity of the mixing and moulding is af- 
forded bj- weighing the briquettes just prior to immersion, or upon re- 
moval from the moist closet. Briquettes which vary in weight more than 
3 per cent, from the average should not be tested. 

Storage of the Test Pieces. 

63. — During the j&rst 24 hours after moulding the test pieces should be 
kept in moist air to prevent them from drying out. 

64. — ^A moist closet or chamber is so easily de\-ised that the use of the 
damp cloth should be abandoned if possible. Covering the test pieces with 
a damp cloth is objectionable, as commonly used, because the cloth may 
drj- out unequally, and, in consequence, the test pieces are not all main- 
tained under the same condition. WTiere a moist closet is not available, 
a cloth may be used and kept uniformly wet by immersing the ends in 
water. It should be kept from direct contact with the test pieces by means 
of a wire screen or some similar arrangement. 

65. — A moist closet consists of a soapstone or slate box or a metal- 
lined wooden box — ^the metal lining being covered with felt and this felt 
kept weL The bottom of the box is so constructed as to hold water, and 
the sides are provided with cleats for holding glass shelves on which to 
place the briquettes. Care should be taken to keep the air in the closet 
uniformly moist. 

66. — After 24 hours in moist air the test pieces for longer periods of 



APPENDICES. 



295 



time should be immersed in water maintained as near 21° Cent. (70° 
Fahr.) as practicable; they may be stored in tanks or pans, which should 
be of non-corrodible material. 

Tensile Strength. 

67. — The tests may be made on any standard machine. A solid metal 
clip, as shown in Fig. 5 (see Fig. y6), is recommended. This clip is to 
be used without cushioning at the points of contact with the test speci- 
men. The bearing at each point of contact should be ^-in. wide, and the 
distance between the center of contact on the same clip should be ij4 ins. 

68. — Test pieces should be broken as soon as they are removed from 
the water. Care shoul-d be observed in centering the briquettes in the 
testing machine, as cross-strains, produced by improper centering, tend 
to lower the breaking strength. The load should not be applied too sud- 
denly, as it may produce vibration, the shock from which often breaks the 
briquette before the ultimate strength is reached. Care must be taken 
that the clips and the sides of the briquette be clean and free from grains 
of sand or dirt, which would prevent a good bearing. The load should 
be applied at the rate of 600 lbs. per minute. The average of the bri- 
quettes of each sample tested should be taken as the test, excluding any 
results which are manifestly faulty. 

Constancy of Volume. 

69. — Significance. — The object is to develop those qualities which tend 
to destroy the strength and durability of a cement. As it is highly essen- 
tial to determine such qualities at once, tests of this character are for 
the most part mr.de in a very short time, and are known, therefore, as 
accelerated tests. Failure is revealed by cracking, checking, swelling or 
disintegration, or all of these phenomena. A cement which remains per- 
fectly sound is said to be of constant volume. 

70. — Methods. — Tests for constancy of volume are divided into two 
•classes: (i) Normal tests, or those made in either air or water main- 
tained at about 21° Cent. (70° Fahr.), and (2) accelerated tests, or those 
made in air, steam or water at a temperature of 45° Cent. (115° Fahr.) 
and upward. The test pieces should be allowed to remain 24 hours in 
moist air before immersion in water or steam, or preservation in air. 

71.— For these tests, pats, about 7V2 cm. (2.95 ins.) in diameter, J^/4 cm. 
(0.49 in.) thick at the center, and tapering to a thin edge, should ho 
made upon a clean glass plate [about 10 cm. (3.94 n^s.) square], from 
cement paste of normal consistency. 

72. — Normal Test. — A pat is immcrscil in water inaintainod as near 
21° Cent. (70° Fahr.) as possible for jS days, and observed at intervalv 
A similar pat is maintained in air at ordinary temperature and observed 
at intervals. 

73._AccELERATED Test.— A pat is exposed in anv convenient wav m an 
atmosphere of steam, above boiling water, in a l.niselv closeil vessel, for 
3 hours. 

74.— To pass these tests satisfactorily, the pats shouM remain hrm and 
hard and show no signs of cracking, distorti n or .lisiutei;r:>tion. 



296 APPENDICES. 

75. — Should the pat leave the plate, distortion may be detected best 
with a straight-edge applied to the surface which was in contact with the 
plate. 

76. — In the present state of our knowledge it cannot be said that ce- 
ment should necessarily be condemned simply for failure to pass the ac- 
celerated tests ; nor can a cement be considered entirely satisfactor}^ sim- 
ply because it has passed these tests. 
Submitted on behalf of the Committee. 

GEORGE S. WEBSTER, 

Chairman. 
RICHARD L. HUMPHREY, 

Secretary. 
Committee. 
George S. Webster, 
Richard L. Humphrey, S. B. Newberry, 
George F. Swain, Clifford Richardson, 

Alfred Noble, W. B. W. Howe, 

Louis C. Sabin, F. H. Lewis. 



APPENDIX B. 



Standard Method for the Chemical Analysis of Cement. 

Adopted by the New York Section of the Society for Chemical Industry, 

January, 1902. 

Solution. 

One-half gram of the finely-powdered substance is to be weighed out 
and, if a limestone or unburned mixture, strongly ignited in a covered 
platinum crucible over a strong blast for 15 minutes, or longer if the blast 
is not powerful enough to effect complete conversion to a cement in this 
time. It is then transferred to an evaporating dish, preferably of platinum 
for the sake of celerity in evaporation, moistened with enough water to 
prevent lumping, and 5 to 10 c. c. of strong HCl added and digested with 
the aid of gentle heat and agitation until solution is complete. Solution 
may be aided by light pressure with the flattened end of a glass rod.* 
The solution is then evaporated to dryness, as far as this may be possible 
on the bath. 

Silica ( SiOs). 

The residue wnthout further heating is treated at first with 5 to 10 c. c. 
of strong HCl, which is then diluted to half strength or less, or upon the 

♦If anything remains undecomposed it should be separated, fused with a little 
NasCOa. dissolved and added to the original solution. Of course a small amount 
of separated non-gelatinous silica is not to be mistaken for undecomposed matter. 



APPENDICES 297 

residue may be poured at once a larger volume of acid of half strength. 
The dish is then covered and digestion allowed to go on for 10 minutes on 
the bath, after which the solution is filtered and the separated silica washed 
thoroughly with water. The filtrate is again evaporated to dryness, the 
residue without further heating, taken up with acid and water and the 
small amount of silica it contains separated on another filter paper. The 
papers containing the residue are transferred wet to a weighed platinum 
crucible, dried, ignited, first over a Bunsen burner until the carbon of the 
filter is completely consumed, and finally over the blast for 15 minutes and 
checked by a further blasting for 10 minutes or to constant weight. The 
silica, if great accuracy is desired, is treated in the crucible with about 
10 c. c. of HFl and four drops of H.^SO^ and evaporated over a low flame 
to complete dryness. The small residue is finally blasted, for a minute or 
two, cooled and weighed. The difference between this weight and the 
weight previously obtained gives the amount of silica.* 

Alumina and Iron (AL2O3 and FcgOs). 

The filtrate, about 250 c. c, from the second evaporation for SiO.„ is 
made alkaline with NH^OH after adding H CI, if need be, to insure a 
total of 10 to 15 c. c strong acid, and boiled to expel excess of NH.^, or 
until there is but a faint odor of it, and the precipitate iron and aluminum 
hydrates, after settling, are washed once by decantation and slightly on the 
filter. Setting aside the filtrate, the precipitate is dissolved in hot dilute 
HCl, the solution passing into the beaker in which the precipitation was 
made. The aluminum and iron are then reprecipitated by NH^OH, boiled 
and the second precipitate collected and washed on the same filter used in 
the first instance. The filter paper, with the precipitate, is then placed in a 
weighed platinum crucible, the paper burned off and the precipitate ignited 
and finally blasted 5 minutes, with care to prevent reduction, cooled and 
weighed as Al^Og -]-■ Fe^O^.f 

Iron (FcgOs). 

The combined iron and aluminum oxides are fused in a platinum cruci- 
ble at a very low temperature with about 3 to 4 grams KKSO^. or 
better NaHSO^, the melt taken up with so much dilute H..SO^, that there 
shall be no less than 5 grams absolute acid and enough water to effect sol- 
ution on heating. The solution is then evaporated and eventually heatcil 
till acid fumes come off copiously. After cooling and redissolving in water 
the small amount of silica is filtered out, weighed and corrected by 1 1 1'l ami 
H^SO^.J The filtrate is reduced by zinc, or preferably by hydrogen .sul- 
phide, boiling out the excess of the latter afterward while passing CO._. 
through the flask, and titrated with permanganate. § The strength of the 
permanganate solution should not be greater than .0040 gr. ln\,0., per e. c. 



*For ordinary control in the plant laboratory this c'orr.HMion ni.iy. perhaps, 
be neglected; the double evaporation never. 

tThis precipitate contains TiC)..., Pi;Or. ..MnnO^. 

tThis correction of AlA. Fe..O:, lor silica siiould not bo mado when the Ml"l 
correction of the main s'ilica ha.s been omitted, unless that slllen was obtained 
by only one evaporation and Hltratioii. After two evaporations and nitra- 
tions 1 to -1 mg. of SiO... are still to be found with (he AloO,, l-e,.t):,. 

§In this way only is the influence of titanium to be avoided and a correct re- 
sult obtained for iron. 



298 APPENDICES. 

Lime (CaO). 

To the combined filtrate from the Al.,0^ -l-Fe^Og precipitate a few drops 
of NH^OH are added, and the solution brought to boiling. To the boil- 
ing solution 20 c. c. of a saturated solution of ammonium oxalate are added, 
and the boiling continued until the precipitated CaC.,0^ assumes a well- 
derined granular form. It is then allowed to stand for 20 minutes, or until 
the precipitate has settled, and then filtered and washed. The precipitate 
and filter are placed wet in a platinum crucible, and the paper burned off 
over a small flame of a Bunsen burner. It is then ignited, redissolved in 
HCl, and the solution made up to 100 c. c. with water. Ammonia is added 
in slight excess, and the liquid is boiled. If a small amount of Al.^O^ 
separates this is filtered out, weighed, and the amount added to that found 
in the first determination, when greater accuracy is desired. The lime is 
then reprecipitated by ammonium oxalate, allowed to stand until settled, 
filtered, and washed,* weighed as oxide by ignition and blasting in a 
covered crucible to constant weight, or determined with dilute standard 
permanganate.t 

Magnesia ( MgO ). 

The combined filtrates from the calcium precipitates are acidified with 
HCl and concentrated on the steam bath to about 150 c. c, 10 c. c. of 
saturated solution of Na (NH JHPO, are added and the solution boiled 
for several minutes. It is then removed from the flame and cooled by 
placing the beaker in ice water. After cooling, NH^OH is added drop by 
drop with constant stirring until the crystalline ammonium-magnesium 
ortho-phosphate begins to form, and then in moderate excess, the stirring 
being continued for several minutes. It is then set aside for several hours 
in a cool atmosphere and filtered. The precipitate is redissolved in hot 
dilute HCl, the solution made up to about 100 c. c, i c. c. of a saturated 
solution of Na(NH^)HPO^ added ,and ammonia drop by drop, with con- 
stant stirring until the precipitate is again formed as described and the 
ammonia is in moderate excess. It is then allowed to stand for about 2 
hours, when it is filtered on a paper or a Gooch crucible, ignited, cooled 
and weighed as ]\Ig., P^O.. 

Alkalies (KoO and NaoO). 
For the determination of the alkalies, the well known method of Prof. 
J. Lawrence Smith is to be followed, either with or without the addition 
of CaCOg with NH^Cl. 

Anhydrous Sulphuric Acid ( SO 3). 

One gram of the substance is dissolved in 15 c. c. of HCl, filtered and 
residue washed thoroughl}'.* 

The solution is made up to 250 c. c. in a beaker and boiled. To the 

♦The volume of wash-water should not be too large; vide Hillebrand. 

tThe accuracy of this method admits of criticism, but its convenience and ra- 
pidity demand its insertion, 

xEvaporation to dryness is unnecessary, unless gelatinous silica should have 
separated and should never be performed on a bath heated by gas; vide Hillebrand. 



APPENDICES. 299 

boiling solution 10 c. c. of a saturated solution of BaCl, is added slowly 
drop by drop from a pipette and the boiling continued until the precipitate 
is well formed, or digestion on the steam bath, may be substituted for 
the boiling. It is then set aside over night, or for a few hours, filtered, ig- 
nited and weighed as BaSO^. 

Total Sulphur. 

One gram of the material is weighed out in a large platinum crucible and 
fused with NaCOg and a little KNO.^, being careful to avoid contamina- 
tion from sulphur in the gases from source of heat. This may be done 
by fitting the crucible in a hole in an asbestos board. The melt is treated 
in the crucible with boiling water and the liquid poured into a tall narrow 
beaker and more hot water added until the mass is disintegrated. The 
solution is then filtered. The filtrate contained in a No. 4 beaker is to be 
acidulated with HCl and made up to 250 c. c. with distilled water, boiled, 
the sulphur precipitated as BaSO^, and allowed to stand over night or for 
a few hours. 

Loss on Ignition.! 

Half a gram of cement is to be weighed out in a platinum crucible, 
placed in a hole in an asbestos board so that about 3-5 of the crucible pro- 
jects below, and blasted 15 minutes, preferably with an inclined flame. 
The loss by weight, which is checked by a second blasting of 5 miiuites, is 
the loss on ignition. 

]\Iay, 1903 : Recent investigations have shown that large errors in re- 
sults are often due to the use of impure distilled water and reagents. 
The analyst should, therefore, test his distilled water by evaporation and 
his reagents by appropriate tests before proceeding with his work. 



APPENDIX C. 



Standard Cement Specifications of the American Society for 
Testing Materials. 

Adopted Noxeniher 14th. kkM- 
General Observations. 

I. — These remarks have been prei)ared with a view of pointing out the 
pertinent features of the various re(|uircments and the pn-eauticMis to he 
observed in the interpretation of the results of the tests. 

2.— The Committee would suggest that the acceptance or reioetion under 
these specifications be based on tests made by an experieucrd person hav- 
ing the proper means for making the tests. 



300 



APPENDICES. 



Specific Gravity. 

3. — Specific gravity is useful in detecting adulteration or under-burning. 
The results of tests of specific gravity are not necessarily conclusive as an 
indication of the quality of a cement, but when in combination with the 
results of other tests may afford valuable indications. 

Fineness. 

4. — The sieves should be kept thoroughly dry. 
Time of Setting. 

5. — Great care should be exercised to maintain the test pieces under as 
uniform conditions as possible. A sudden change or wide range of tempera- 
ture in the room in which the tests are made, a very dry or humid atmos- 
phere, and other irregularities vitally affect the rate of setting. 

Tensile Strength. 

6. — Each consumer must fix the minimum requirements for tensile 
strength to suit his own conditions. They shall, however, be within the 
limits stated. 

Constancy of Volume. 

7. — The tests for constancy of volume are divided into two classes, the 
first normal, the second accelerated. The latter should be regarded as a 
precautionary test only, and not infallible. So many conditions enter into 
the making and interpreting of it that it should be used with extreme care. 

8. — In making the p?ts the greatest care should be exercised to avoid 
initial strains due to moulding or to too rapid drying-out during the first 
twenty-four hours. The pats should be preserved under the most uniform 
conditions possible, and rapid changes of temperature should be avoided. 

9. — The failure to meet the requirements of the accelerated tests need not 
be sufficient cause for rejection. The cement may, however, be held for 
twenty-eight days, and a retest made at the end of that period. Failure to 
meet the requirements at this time should be considered sufficient cause 
for rejection, although in the present state of our knowledge it cannot be 
said that such failure necessarily indicates unsoundness, nor can the cement 
be considered entirely satisfactory simply because it passes the tests. 

General Conditions. 

I. — All cement shall be inspected. 

2. — Cement may be inspected either at the place of manufacture or on the 
work. 

3. — In order to allow ample time for inspecting and testing, the cernent 
should be stored in a suitable weather-tight building having the floor prop- 
erly blocked or raised from the ground. 

4. — The cement shall be stored in such a manner as to permit easy access 
for proper inspection and identification of each shipment. 

5. — Every facility shall be provided by the contractor and a period of at 
least twelve days allowed for the inspection and necessary tests. 

6. — Cement shall be delivered in suitable packages with the brand and 
name of marufacturer plainly marked thereon. 



APPENDICES. 301 

7, A bag of cement shall contain 94 pounds of cement net. Each barrel 
of Portland cement shall contain 4 bags, and each barrel of natural cement 
shall contain 3 bags of the above net weight. 

8. — Cement failing to meet the seven-day requirements may be held 
awaiting the results of the twenty-eight day tests before rejection. 

9. — All tests shall be made in accordance with the methods proposed by 
the Committee on Uniform Tests of Cement of the American Society of 
Civil Engineers, presented to the Society January 21, 1903, and amended 
January 20, 1904, with all subsequent amendments thereto. 

10. The acceptance or rejection shall be based on the following re- 
quirements : 

Natural Cement. 

11. Definition. This term shall be applied to the finely pulverized pro- 
duct resulting from the calcination of an argillaceous limestone at a tem- 
perature only sufficient to drive off the carbonic acid gas. 

Specific Gravity. 

12. — The specific gravity of the cement thoroughly dried at 100° Cent., 
shall be not less than 2.8. 

Fineness. 
13. — It shall leave by weight a residue of not more than 10% on the No. 
100, and 30% on the No. 200 sieve. 

Time of Setting. 
14. — It shall develop initial set in not less than ten minutes, and hard 
set in not less than thirty minutes, nor more than three hours. 
Tensile Strength. 
15. — The minimum requirements for tensile strength for briquettes one 
inch square in cross section shall be within the following limits, and shall 
show no retrogression in strength within the periods specified :* 

Age. Neat Cement. Strength. 

24 hours in moist air .So- 100 lbs. 

7 days ( I day in moist air, 6 days in water) 100-200 " 

28 days ( I day in moist air, 27 days in water) 200-300 " 

One Part Cement, Three Parts Standard Sand. 

7 days ( i dayMn moist air, 6 days in water) 25- 75 " 

28 days (i day in moist air, 27 days in water) 75- 150 '* 

Constancy of Volume. 

16. — Pats of neat cement about throe inches in diameter, one-half inch 
thick at center, tapering to a thin edge, shall be kept in moist air for a 
period of twenty-four hours. 

(a) A pat is then kept in air at normal tcmi)eraturc. 

(b) Another is kept in water maintained as near 70' j-'ahr. as practi- 
cable. 

17. — These pats are observed at intervals for at least -'8 days, ami. to 

*For example the minimum requir.Mneiit for tli»- twenty-four hour neat ce- 
ment test should be some spefifled value within tbo limits of M and UK) 
pounds, and so on for each period staled. 



302 APPENDICES. 

satisfactorily pass the tests, should remain firm and hard and show no 
signs of distortion, checking, cracking or disintegrating. 
Portland Cement. 
i8. — Definition. — This term is applied to the finely pulverized prod- 
uct resulting from the calcination to incipient fusion of an intimate mix- 
ture of properly proportioned argillaceous and calcareous materials, and 
to which no addition greater than 3% has been made subsequent to 
calcination. 

Specific Gravity. 

19. — The specific gravity of the cement, thoroughly dried at 100° Cent, 
shall be not less than 3.10. 

Fineness. 

20. — It shall leave by weight a residue of not more than 8% on the 
No. 100, and not more than 25% on the No. 200 sieve. 
Time of Setting. 
21. — It shall develop initial set in not less than thirty minutes, but must 
develop hard set in not less than one hour, nor more than ten hours. 
Tensile Strength. 
22. — The minim.um requirements for tensile strength for briquettes one 
inch square in section shall be within the following limits, and shall show 
no retrogression in strength within the periods specified."^ 
Age. Neat Cement. Strength. 

24 hours in moist air 150-200 lbs. 

7 days (i day in moist air, 6 days in water) 450-550 " 

28 days (i day in moist air, 27 days in water) 550-650 " 

One Part Cement, Three Parts Sand. 

7 days (i day in moist air, 6 days in water) 150-200 " 

28 days (i day in moist air, 27 days in water) 200-300 " 

Constancy of Volume. 

23. — Pats of neat cement about three inches in diameter, one-half inch 
thick at the centre, and tapering to a thin edge, shall be kept in moist air 
for a period of twenty-four hours. 

(a) A pat is then kept in air at normal temperature and observed at 
intervals for at least 28 days. 

(b) Another pat is kept in water maintained as near 70° Fahr. as prac- 
ticable, and observed at intervals for at least 28 days. 

(c) A third pat is exposed in any convenient way in an atmosphere 
of steam, above boiling water, in a loosely closed vessel for five hours. 

24. — These pats, to satisfactorily pass the requirements, shall remain 
firm and hard and show no signs of distortion, checking, cracking or 
disintegrating. 

Sulphuric Acid and Magnesia. 

25. — The cement shall not contain more than 1.75% of anhydrous sul- 
phuric acid (SO3), nor more than 4% of magnesia (MgO). 

♦For example the minimum requirement for the twenty- four hour neat cement 
test should be some specified value within the limits of 150 and 200 pounds, and 
so on for each period stated. 



APPENDICES. 303 



APPENDIX D 



U. S. Army Standard Specifications.* 

Recommended by the Board of Engineer Officers on Testing Hydraulic Ce- 
ments, for use in the Engineer Department, U. S. Army. Major William L. 
Marshall, Major Smith S. Leach, Captain Spencer Cosby, Corps of Engineers, 
Members of Board. 

Specifications for American Portland Cement. 

(1) The cement shall be an American Portland, dry, and free from 
lumps. By a Portland cement is meant the product obtained irom the 
heating or calcining up to incipient fusion of intimate mixtures, either 
natural or artificial, of argillaceous with calcareous substances, the calcined 
product to contain at least 1.7 times as much of lime, by weight, as of 
the materials which give the lime its hydraulic properties, and to be finely 
pulverized after said calcination,* and thereafter additions or substitutions 
for the purpose only of regulating certain properties of technical import- 
ance to be allowable to not exceeding 2 per cent, of the calcined product. 

(2) The cement shall be put up in strong, sound barrels well lined 
with paper, so as to be reasonably protected against moisture, or in stout 
cloth or canvas sacks. Each package shall be plainly labeled with the 
name of the brand and of the manufacturer. Any package broken or 
containing damaged cement may be rejected or accepted as a fractional 
package, at the option of the United States agent in local charge. 

(3) Bidders will state the brand of cement which they propose to fur- 
nish. The right is reserved to rejeci a tender for any brand which has 
not established itself as a high-grade Portland cement and has not for 
three years or more given satisfaction in use under climatic or other 
conditions of exposure of at least equal severity to those of the work 
proposed. 

(4) Tenders will be received only from manufacturers or their author- 
ized agents. 

(The following paragraph will be substituted for paragraphs 3 and 4 
above when cement is to be furnished and placed by the contractor: 

No cement will be allowed to be used except established brands of high- 
grade Portland cement which have been made by the same mill and in 
successful use under similar climatic conditions to those of the proposed 
work for at least three years.) 

(5) The average weight per barrel shall not be less than 375 ptnnuls 
net. Four sacks shall contain one barrel of cement. If the weight, as 
determined by test weighings, is found to be below 375 pounds per barrel, 
the cement may be rejected, or, at the option of the engineer officer in 
charge, the contractor may be required to supply, free of cost to the 
United States, an additional amount of cement equal to the shortage. 

(b) Tests may be made of the fineness, specific gravity, soundness, time 
of setting, and tensile strength of the cement. 



•Professional Papers No. 2S, Corps of Englnoers. U. 3 .\rtTiy. 



304 



APPEX DICES. 



(7) Fineness. — Ninety-two per cent, of the cement must pass through 
a sieve made of No. 40 wire, Stubb's gauge, having 10.000 openings per 
square inch. 

(8) Specific Gravity. — The specific gravity of the cement as deter- 
mined from a sample which has been carefully dried, shall be between 
3.10 and 3.25. 

(9) Soundness. — To test the soundness of the cement, at least two pats 
of neat cement mixed for five minutes with 20 per cent, of water by 
weight shall be made on glass, each pat about 3 inches in diameter and 
one-half inch thick at the center, tapering thence to a thin edge. The pats 
are to be kept under a wet cloth until finally set, when one is to be 
placed in fresh water for twenty-eight days. The second pat will be 
placed in water which will be raised to the boiling point for six hours, 
then allowed to cool. Neither should show distortion or cracks. The 
boiling test may or may not reject at the option of the engineer officer 
in charge. 

(10) Time of Setting. — The cement shall not acquire its initial set in 
less than forty-five minutes and must have acquired its final set in ten 
hours. 

(The following paragraph will be substituted for the above in case a 
quick-setting cement is desired : 

The cement shall not acquire its initial set in less than twenty nor more 
than thirty minutes, and must have acquired its final set in not less than 
forty-five minutes nor more than two and one-half hours.) 

The pats made to test the soundness may be used in determining the 
time of setting. The cement is considered to have acquired its initial set 
when the pat Avill bear, without being appreciably indented, a wire one- 
twelfth inch in diameter loaded to weigh one-fourth pound. The final set 
has been acquired when the pat will bear, without being appreciably in- 
dented, a wire one-twenty-fourth inch in diameter loaded to weigh i 
pound. 

(11) Tensile Strength. — Briquettes made of neat cement, after being 
kept in air for twent3'-four hours under a wet cloth and the balance of 
the time in water, shall develop tensile strength per square inch as follows: 

After seven days, 450 pounds ; after twenty-eight days, 540 pounds. 

Briquettes made of i part cement and 3 parts standard sand, by weight, 
shall develop tensile strength per square inch as follows : 

After seven days, 140 pounds; after twenty-eight days. 220 pounds. 

(In case quick-setting cement is desired, the following tensile strengths 
shall be substituted for the above: 

Neat briquettes : After seven days, 400 pounds ; after twenty-eight days, 
480 pounds. 

Briquettes of i part cement to 3 parts standard sand: After seven 
days, 120 pounds; after twenty-eight days, 180 pounds.) 

(12) The highest result from each set of briquettes made at any one 
time is to be considered the governing test. Any cement not showing 
an increase of strength in the twenty-eight day tests over the seven-day 
tests will be rejected. 



APPENDICES. 305 

(13) When making briquettes neat cement will be mixed with 20 per 
cent, of water by weight, and sand and cement with 12^ per cent, of water 
by weight. After being thoroughly mixed and worked for five minutes, 
the cement or mortar will be placed in the briquette mold in four equal 
layers, and each layer rammed and compressed by thirty blows of a soft 
brass or copper rammer three-quarters of an inch in diameter (or seven- 
tenths of an inch square, with rounded corners), weighing i pound. It 
is to be allowed to drop on the mixture from a height of about half an 
inch. When the ramming has been completed the surplus cement shall be 
struck off and the final layer smoothed with a trowel held almost hori- 
zontal and drawn back with sufficient pressure to make its edge follow 
the surface of the mold. 

(14) The above are to be considered the minimum requirements. Un- 
less a cement has been recently used on work under this office, bidders 
will deliver a sample barrel for test before the opening of bids. If this 
sample shows higher tests than those given above, the average of tests 
made on subsequent shipments must come up to those found with the 
sample. 

(15) A cement may be rejected in case it fails to meet any of the above 
requirements. An agent of the contractor may be present at the mak- 
ing of the tests, or, in case of the failure of any of them, they may be re- 
peated in his presence. If the contractor so desires, the engineer officer in 
charge may, if he deem it to the interest of the United States, have any 
laboratory in the manner herein specified. All expenses of such tests to be 
or all of the tests made or repeated at some recognized standard testing 
paid by the contractor. All such tests shall be made on samples furnished 
by the engineer officer from cement actually delivered to him. 

Specifications for Natural Cement. 

(i) The cement shall be a freshly packed natural or Rosendale, dry, 
and free from lumps. By Natural cement is meant one made by calcin- 
ing natural rock at a heat below incipient fusion, and grinding the product 
to powder. 

(2) Same as Portland (2). 

(3) Bidders will state the brand of cement which they propose to fur- 
nish. The right is reserved to reject a tender for any brand which has 
not given satisfaction in use under climatic or other conditions of expo- 
sure of at least equal severity to those of the work proposed. 

(4) Tenders will be received only from manufacturers or their author- 
ized agents. 

(The following paragraph will be substituted for paragraphs 3 and 4 
above when cement is to be furnished and placed by the contractor: 

No cement will be allowed to be used except established brands of 
high-grade natural cement which have been in successful use under simi- 
lar climatic conditions to those of the proposed work.) 

(5) The average net weight per barrel shall not be less than 300 pounds. 
(West of the Allegheny Mountains this may be 265 pounds.) . . . 
sacks of cement shall have the same weight as i barrel. It the average 



3o6 APPENDICES. 

net weight, as determined by test weighings, is found to b-e below 300 
pounds (265 pounds) per barrel, the cement may be rejected, or, at the 
option of the engineer officer in charge, the contractor may be required 
to supply free of cost to the United States an additional amount of cement 
equal to the shortage. 

(6) Tests may be made of the nneness, time of setting, and tensile 
strength of the cement. 

(^7) Fineness. — At least 80 per cent of the cement must pass through 
a sieve made of Xo. 40 wire, Stubb's gauge, having 10.000 openings per 
square inch. 

(8) Time of Settixg. — The cement shall not acquire its initial set in 
less than twenty minutes and must have acquired its final set in four 
hours. 

(9) The time of setting is to be determined from a pat of neat cement 
mixed for five minutes with 30 per cent, of water b}- weight and kept un- 
der a wet cloth until finally set. The cement is considered to have 
acquired its initial set when the pat will bear, without being appreciably 
indented, a wire one- twelfth inch in diameter loaded to weigh one- fourth 
pound. The final set has been acquired when the pat will bear, without 
being appreciably indented, a wire one-twent\--fourth inch in diameter 
loaded to weigh i pound. 

(10) Tensile Strength. — Briquettes made of neat cement shall de- 
velop the following tensile strengths per square inch after having been 
kept in air for twenty-four hours under a wet cloth and the balance 
of the time in water : 

At the end of seven days. 90 pounds ; at the end of twenty-eight days, 
200 pounds. 

Briquettes made of one part cement and one part standard sand by 
weight shall develop the following tensile strengths per square inch : 

After seven days, 60 pounds ; after twentj-eight da3-s, 150 pounds. 

(11) Same as Portland (12). 

(12) Same as Portland (13) except that 30 and 17 per cent of water are 
used for neat and sand mixtures respectiveh". 

(13) Same as Portland (14). 

(14) Same as Portland (15). 

Specifications for Puzzolan Cement. 

(i) The cement shall be a Puzzolan of uniform quality', finely and freshly 
ground, drj-, znd free from lumps, made by grinding together without 
subsequent calcination granulated blast-furnace slag with slaked lime. 

(2) Same as Portland (2). 

(3) Bidders will state the brand of cement which they propose to fur- 
nish. The right is reserved to reject a tender for any brand which has 
not given satisfaction in use under climatic or other conditions of expo- 
sure of at least equal severit\- to those of the work proposed, and for 
any brand from cement works that do not make and test the slag used in 
the cement 



APPENDICES. 



307 



(4) Tenders will be received only from manufacturers or their author- 
ized agents. 

(The following paragraph will be substituted for paragraphs 3 and 4 
above when cement is to be furnished and placed by the contractor: 

No cement will be allowed to be used except established brands of high- 
grade Puzzolan cement which have been in successful use under similar 
climatic conditions to those of the proposed work and which come from 
cement works that make the slag used in the cement.) 

(5) The average weight per barrel shall not be less than 330 pounds net 
Four sacks shall contain i barrel of cement. If the weight as determined 
by test weighings is found to be below 330 pounds per barrel, the cement 

■may be rejected or, at the option of the engineer officer in charge, the con- 
tractor may be required to supply, free of cost to the United States, an 
additional amount of cement equal to the shortage. 

(6) Tests may be made of the fineness, specific gravity, soundness, time 
of setting, and tensile strength of the cement. 

(7) Fineness. — Ninety-seven per cent, of the cement must pass through 
a sieve made of No. 40 wire, Stubb's gauge, having io,odo openings per 
square inch. 

(8) Specific Gravity. — The specific gravity of the cement as determined 
from a sample which has been carefully dried, shall be between 2.7 and 2.8. 

(9) Soundness. — To test the soundness of cement, pats of neat cement 
mixed for five minutes with 18 per cent, of water by weight shall be made 
on glass, each pat about 3 inches in diameter and one-half inch thick at the 
center, tapering thence to a thin edge. The pats are to be kept under wet 
cloths until finally set, when they are to be placed in fresh water. They 
should not show distortion or cracks at the end of twenty-eight days. 

(10) Time of Setting. — The cement shall not acquire its initial set in 
less than forty-five minutes and shall acquire its final set in ten hours. 
The pats made to test the soundness may be used in determining the time 
of setting. The cement is considered to have acquired its initial set when 
the pat will bear, without being appreciably indented, a wire one-twolfth 
inch in diameter loaded to one-fourth pound weight. The final set has 
been acquired when the pat will bear, without being appreciably indented, 
a wire one twenty-fourth inch in diameter loaded to i pound weight. 

(11) Tensile Strength. — Briquettes made of neat cement, after being 
kept in air under a wet cloth for twenty-four hours and the balance of the 
time in water, shall develop tensile strength per s(iuaro inch as follows: 

After seven days, 350 pounds; after twentv-eight days. 50c) pounds. 
Briquettes made of one part cement and tliri-e parts standard sanil by 
weight shall develop tensile strength per s(|iiare inch as follows: 
After seven days, 140 pounds; after twenty-eight days, jjo pounds. 

(12) Same as Portland (12). 

(13) Same as Portland (13) except thai iS and 10 per cent, of water arc 
used for neat and sand mixtures respectively. 

(14) Same as Portland (14). 

(15) Same as I'orll.ird ( i.s). 



3o8 APPEX DICES. 

APPENDIX E. 



British Standard Specifications for Portland Cement. 

Issued by the Engineering Standards Committee, supported by the Institution 
of Civil Engineers, The Institution of Mechanical Engineers, the Institution of 
Naval Architects, the Iron and Steel Institute and the Institution of Electrical 
Engineers. 

Quality and Preparation. 

I. — The cement is to be prepared by intimateh- mixing together calcare- 
ous and argillaceous materials, burning them at a clinkering temperature 
and grinding the resulting clinker. Xo addition of an}- material is to be 
made after burning, except when desired by the manufacturer, and if not 
prohibited in writing by the consumer, in which case calcium sulphate or 
water may be used. The cement, if watered, shall contain not more than 2 
per cent, of water, whether that water has been added or has been natur- 
ally absorbed from the air. If calcium sulphate is used, not more than 2 
per cent, calculated as anhydrous calcium sulphate of the weight of the ce- 
ment shall be added. 

Sampling and Preparation for Testing and Analysis. 

2. — As soon as the cement has been bulked at the makers' works.* or on 
the works in connection with which the material is to be used, at the con- 
sumer's option, samples for testing are to be taken from each parcel, each 
sample consisting of cement frcm at least twelve different positions in the 
same heap, so distributed as to ensure, as far as is practicable, a fair aver- 
age sample of the whole parcel, all to be mixed together and the sample for 
testing to be taken therefrom. 

3. — Before gauging the tests, the sample so obtained is to be spread out 
for a depth of 3 ins. for 24 hours, in a temperature of 58 to 64 degrees 
Fahrenheit. 

4. — In all cases where consignments are of lOO tons and upwards, sam- 
ples selected as above from each consignment, either at the makers' works 
or after delivery at the works where the cement is to be used, are to be 
sent for expert testing and for chemical analysis. In no case is cement 
so tested and analyzed to be accepted, or used, unless previously certified 
in writing by the consumer to be of satisfactory quality. Payment for 
such tests and analysis to be made by the consumer, the manufacturer sup- 
plying the cement r quired for the same, free of charge. 

When consignments of less than 100 tons have to be supplied, the makers 
shall, if required, give certificates for each deliver3\ to the effect that such 
cement complies with the terms of this standard specification, with regard 
to qualit}-, tests, and chemical analysis, no payment being made by the 
consumer for such certificate, nor for the making of such tests and ana- 
lyses. 

5. — Should it be deemed more convenient by the consumers, that the 



♦Should the consumer desire to stipulate for any special quantity, the size of 
the heap should be stated. 



APPENDICES. 309 

samples for testing should be taken at the maker's works before delivery, 
the latter are, in that event, to afford full facilities to the inspector, who 
may be appointed by the consumers to sample the cement as he may desire 
at the maker's works, and subsequently to identify each parcel as it may be 
despatched, with that sampled by him. No parcel is to be sent away, unless 
a written order has been previously received by the makers from the 
said consumer to the effect that the material in question has been ap- 
proved. 

Fineness and Sieves. 

6. — The cement shall be ground to comply with the following degrees of 
fineness, viz : 

The residue on a sieve 76 X 76 = 5,776 meshes per square inch is not to 
exceed 5 per cent. 

The residue on a sieve 180 X iSo" =^ 32,400 meshes per square inch is 
not to exceed 22^/^ per cent. 

The sieves are to be prepared from standard wire, the size of the wire 
for the 5,776 mesh is to be .0044 inch, and for the 32,400 mesh, .0018 inch. 
The wire shall be woven (not twilled), the cloth being carefully mounted 
on the frames without distortion. 

Specific Gravity. 

7. — The specific gravity of the cement shall be not less than 3.15 when 
sampled and hermetically sealed at the maker's works, nor less than 3.10. 
if sampled after delivery to the consumer. 

Chemical Composition. 

8. — The cement is to comply with the following conditions as to its 
chemical composition. There shall be no excess of lime, that is to say, the 
proportion of lime shall be not greater than is necessary to saturate the 
silica and alumina present. The percentage of insoluble residue shall not 
exceed 1.5 per cent. ; that of magnesia shall not exceed 3 per cent., and 
that of sulphuric anhydride shall not exceed 2.5 per cent. 

Tensile Tests. 

9. — The quantity of water used in gauging shall be appropriate to the 
quality of the cement, and shall be so proportioned that when the cement 
is gauged it shall form a smooth, easily worked paste, that will leave the 
trowel cleanly in a compact mass. Fresh water is to be used for gauging, 
the temperature thereof, and of the test room at the time the said (^H^ra- 
tions are performed, being from 58 to 64 degrees Fahrenheit. 

The cement gauged as above is to be filled, witiunit mechanical ramming, 
into moulds of the form shown in h'ig. 140 on the annexed sketch, each 
movild resting upon an iron plate until the cement has set. W'hon the 
cement has set sufficiently to enable the mould to be removed without in- 
jury to the briquette, such removal is to be effected. The said briquette 
shall be kept in a damp atmosphere and placed in fresh water -'4 liours 
after gauging, and kept there until broken, the water in which the test 
briquettes are submerged being renewed every seven davs. and the tem- 
perature thereof maintained between 5S and ()4 degrees l\\hreu!ieit. 



3JO 



APPENDICES. 



Neat Tests. 

10. — Briquettes of neat cement of the shape shown in Fig. 140 and an- 
nexed thereto are to be gauged for breaking at 7 and 28 days, respec- 
tively, six briquettes for each period. The average tensile strength of the 
six briquettes shall be taken as the accepted tensile strength for each 

|<- -/."75 H 

Iz-^^-STiT ... _.^ ^^„ 



GfifO- 





Plan. 
Y0."7S^- I!Z0 -'»^0"75^ ,-0.50 Rad. 




Fig. A. 
Dimensions of Briquette. 

Fig. 140. 



E\eva+ion. 
Fiq.B, Details Off Jaws -for Holdrng 
Briquette. 

Fig. 141. 



period. For breaking, the briquette is to be held in strong metal jaws, of 
the shape shown in Fig. 141 on the annexed sketch, the briquettes being 
slightly greased where gripped by the jaws. The load must then be 
steadily and uniformly applied, starting from zero, increasing at the rate 
of 100 pounds in 12 seconds. The briquettes are to bear on the average 
not less than the following tensile stresses before breaking: 

7 days from gauging 400 lbs. per sq. inch of section. 

28 days from gauging 500 lbs. per sq. inch of section. 

The increase from 7 to 28 days shall not be less than : 
25% when the 7-day test falls between 400 lbs. to 450 lbs. per sq. in. 
20% when the 7-day test falls between 450 lbs. to 500 lbs. per sq. in. 
15% when the 7-day test falls between 500 lbs. to 550 lbs. per sq. in. 
10% when the 7-day test falls between 550 lbs. per sq, in. or upwards. 

Sand Tests. 

II. — The cement shall also be tested by means of briquettes prepared 
from one part of cement to three parts of weight of dry standard sand, 
the said briquettes being of the shape described for the neat cement tests, 
the mode of gauging, filling the moulds, and breaking the briquettes is 
also to be similar. The proportion of water used shall be such that the 
mixture is thoroughly wetted, and there shall be no superfluous water 
when the briquettes are formed. The cement and sand briquettes are to 
bear the following tensile stresses : 

7 days from gauging 120 lbs. per sq. inch of section. 

28 days from gauging 225 lbs. per sq. inch of section. 

[ The increase from 7 to 28 days shall not be less than 20 per cent. 



APPENDICES. 311 

The standard sand referred to above is to be obtained from Leighton 
Buzzard. It must be thoroughly washed, dried and passed through a sieve 
of 20 X 20 meshes per square inch, and must be retained on a sieve of 
30 X 30 meshes per square inch, the wires of the sieve being .0164 and 
.0108 inch, respectively. 

Setting Time. 

12.— There shall be three distinct gradations of setting time, which shall 
be designated as "quick," "medium," and "slow."* 

Quick— The setting time shall be not less than ten minutes, or more 
than 30 minutes. 

Medium— The setting time shall be not less than half an hour, or more 
than two hours. 

Slow— The setting time shall be not less than two hours, or more than 
five hours.* 

The temperature of the air in the test room at the time of gauging 
and of the water used is to be between 58 and 64 degrees Fahrenheit. 

The cement shall be considered as "set" when a needle having a flat 

(5p//f CylinS^Faf Springr Brass "• 
or other Suitable Metal 
about ^"""^In thickness 



•a 



II 



1 



165"".":. >f 

Plan. 



I 



Elevation. 



Apparatus tor Conducting the "Le Chatelrer "Test. 
Fig. 142. 

end 1-16 inch square, weighing in all 2^ lbs., fails to make an impression 
when its point is applied gently to the surface. 

Soundness. 

13. — The cement shall be tested by the Le Chatelier method, and is in 
no case to show a greater expansion than 12 millimetres after 24 hours' 
aeration and 6 millimetres after seven days' aeration. 

NOTE. — The apparatus for conducting the Le Chatelier te.st (Fig. 142) 
consists of a small split cylinder of spring brass or other suitable metal 
of 0.5 millimetre (0.197 inch) in thickness, 30 millimetres (T.1875 inches) 
internal diameter, and 30 millimetres high, forming the mould, to which 
on either side of the split are attached two indicators 165 millimetres (6.5 
inches) long from the center of the cylinder, with pointid- ends A A, as 
shown upon the sketch. 

In conducting the test, the mould is to be placed upon a small piece 
of glass and filled with cement gauged in the usual wav. care being taken 
to keep the edges of the moulds gently together while this operation is 

♦When a specially slow settlriR ceniont Is required, the minimum time of set- 
\.'--z, shall be specified. 



312 APPENDICES. 

being performed. The mould is then covered with another glass plate, 
a small weight is placed on this and the mould is immediately placed in 
water at 58 to 64 degrees Fahrenheit, and left there for 24 hours. 

The distance separating the indicator points is then measured, and the 
mould placed in cold water, which is brought to a boiling point in 15 to 
30 minutes, and kept boiling for six hours. After cooling, the distance 
between the points is again measured; the difference between the two 
measurements represents the expansion of the cement, which must not 
exceed the limits laid down in this specification. 

14. — The tests and analyses hereinbefore referred to shall in no case 
relate to a larger quantity of cement than 250 tons sampled at one time. 

Acceptance. 

15. — No cement is to be approved or accepted unless it fully complies 
with the foregoing conditions. 



APPENDIX F, 



Standard Specifications for Portland Cement. 

Adopted by the Canadian Society of Civil Engineers. 
Report submitted, January 27th, 1903. 
Committee:— Dr. H. T. Bovey (chairman), Messrs. M. J. Butler, C. B. Smith, 
T. Monro, P. A. Peterson, C. H. Rust, G. A. Mountain and J. A. Duff 

The whole of the cement is to be well-burned, pure Portland cement, of 
the best quality, free fro^m free-lime, slag, dust, or other foreign material. 

(i) Fineness. — The cement shall be ground so fine that the residue on 
a sieve of 10,000 meshes to the square inch shall not exceed ten per cent, 
of the whole by weight, and the whole of the cement shall pass a sieve of 
2,500 meshes to the square inch. 

(2) Specific Gravity. — The specific gravity of the cement shall be at 
least 3.09 and shall not exceed 3.25 for fresh cement ; the term "fresh" 
being understood to apply to such cements as are not more than two 
months old. 

(3) Tests. — The cement shall be subjected to the following tests: 

(a) BLOWiNq Test. — ]\Iortar pats of neat cement thoroughly worked, 
shall be trowelled upon, carefully cleaned, 5 in. by 2^-in. ground glass, 
plates. The pats shall be about ^ in. thick in the center and worked off 
to the sharp edges at the four sides. They shall be covered with a damp 
cloth and allowed to remain in. the air until set, after which they shall be 
placed in vapor in a tank, in which the water is heated to a temperature 
of 130° Fahr. After remaining in the vapor six hours, including the time 



APPENDICES. 



3^3 



of setting in air, they shall be immersed in the hot water and allowed to 
remain there for eighteen hours. After removal from the water the sam- 
ples shall not be curled up, shall not have fine hair cracks, nor large 
expansion cracks, nor shall they be distorted. If separated from the glass, 
the samples shall break with a sharp, crisp ring. 

(b) Tensile Test. (Neat Cement.) — Briquettes made of neat cement, 
mixed with about twenty per cent, of water, by weight, after remaining 
one day in air, in a moist atmosphere, shall be immersed in water, and 
shall be capable of sustaining a tensile stress of 250 lbs. per square inch 
after submersion for two days ; 400 lbs. per square inch after submersion 
for six days ; 500 lbs. per square inch after submersion for twenty-seven 
days. The tensile test shall be considered as the average of the strength 
of five briquettes, and any cement showing a decrease in tensile strength 
on or before the twenty-eighth day shall be rejected. 

(Sand and Cement). — The sand for standard tests shall be clean quartz, 
crushed so that the whole shall pass through a sieve of 400 meshes to the 
square inch, but shall be retained on a sieve of 900 meshes per square inch. 
The sand and cement shall be thoroughly mixed dry, and then about ten 
per cent, of their weight of water shall be added, when the briquettes are 
to be formed in suitable moulds. After remaining in a damp chamber 
for twenty-four hours the briquettes shall be immersed in water, and 
briquettes made in the proportion of one of cement to three of sand, by 
weight, shall bear a tensile stress of 125 lbs. per square inch after sub- 
mersion for six days, and 200 lbs. per square inch after submersion for 
twenty-eight days. Sand and cement briquettes shall not show a decrease 
in tensile strength at the end of twenty-eight days, or subsequently. 

(4) The manufacturer shall, if required, supply chemical analyses of 
the cement. 

(5) Packing. — The cement shall be packed either in stout air and water- 
tight casks, carefull}^ lined with strong brown paper, or in strong air and 
water-tight bags. 

(6) The manufacturer shall give a certificate with each shipment of ce- 
ment stating (i) the date of manufacture; (2) the tests and analyses 
which have been obtained for the cement in question at the manufacturer's 
laboratory; (3) that the cement does not contain any adulterations. 

(Note: This specification is followed by a standard method oi testing.) 



APPENDIX G 



Bibliography. 

A brief list of the books, in the I'ji.uli.sh language, on cement and con- 
cretes, best suited for referonci'. with tlie essential features of each: 
Bleninger., A. V.. The .Manufacture of ll>(lraulic Cenunts. JMMirtli < •■■ - 



314 



APPENDICES. 



Bulletin No. 3, State Geological Survey of Ohio, 1904. 

(Chemistry of cements and cement materials, and methods of manu- 
facture.) 
Brown, Charles C. Directory of American Cement Industries and Hand 

Book for Cement Users. Municipal Engineering Co., Indianapolis, 

Ind. — Published yearly. 

(Directory of brands, manufacturers, agents, users, with other data on 
the industry.) 

Buel, A. W. and C. S. Hill. Reinforced Concrete. Engineering News 
Publishing Co., New York, 1904. 

(Mathematical discussion, and practical consideration of constructions 
of reinforced concrete.) 
Burr, William H. The Elasticity and Resistance of the Materials of En- 
gineering. John iWilev & Sons, New York, 1903. 
(Chiefly mathematical, little practical data.) 
Butler, David B. Portland Cement, Its Manufacture, Testing and Use. 
Spon, London, 1899. 
(English practice in manufacture and testing.) 
Cement Industry, The. The Engineering Record, New York, 1900. 

(Descriptions of plants and processes.) 
Considere, A. Experimental Researches on Reinforced Concrete, trans- 
lated and arranged by Leon S. Moisseiff. McGraw Publishing Co., 
New York, 1903. 
(Experiments and data on reinforced concrete.) 

Cummings, Uriah. American Cements. Rogers and Manson, Boston, 1898. 

(Historical data, and discussion of natural cements.) 
Eckel, Edwin C. Cements, Limes, and Plasters. John Wiley & So-ns, 
New York, 1905. 

(Cement materials and processes of manufacture.) 
Falk, Myron S. Cements, Mortars and Concretes. Myron C. Clark, New 
York, 1904. 
(Data on investigations of physical properties.) 
Gillette, Halbert P. Hand-book of Cost Data. Myron C. Clark, New 

York, 1905. (Costs of Concrete and Concrete-Steel Structures.) 
Grant, John. Portland Cement; Its Nature, Tests, and Uses. Spon, Lon- 
don, 1875. 
(Data on strength of cement — chiefly of historic interest.) 
Johnson, J. B. The Materials of Construction. John Wiley & Sons, New 
York, 1898. 
(Mathematical discussion, general description, and much valuable data.) 
Le Chatelier, H. Experimental Researches on the Constitution of Hy- 
draulic Mortars, translated by Joseph L. Mack. McGraw Publishing 
Co., New York, 1905. 
(Chemical and mineralogical study of cement composition.) 
Marsh, Charles F, Reinforced Concrete. D. Van Nostrand Co., New 
York, 1904. 
(Theoretical and practical discussion of concrete structures.) 



APPENDICES. 



315 



Meade, Richard K. The Examination of Portland Cements. The Chemi- 
cal Publishing Co., Easton, Pa., 1901. 
(Methods of chemical analysis.) 
Redgrave, Gilbert R. and C. Spackman. Calcareous Cements : Their 
Nature and Use. Chas. Griffin & Co., London, 1905. 
(Historical data, and English methods of manufacture and testing.) 
Sabin, Louis C. Cement and Concrete. McGraw Publishing Co., New 
York, 1905. 
(Valuable data on the properties of cement, and their application to 
practical construction.) 
Spalding, Frederick P. Hydraulic Cement : Its Properties, Testing and 
Use. John Wiley & Sons, New York, 1897. 
(The nature and testing of cement — no data.) 
Taylor, Frederick W. and Sanford E. Thompson. A Treatise on Concrete, 
Plain and Reinforced. John Wiley & Sons, New York, 1904. 
(Data on cements and concretes, and practical application to construc- 
tion work.) 



i 



INDEX 



Page. 

Abrasion, tests of 219 

Accelerated tests. (See Soundness.) 
Accuracy obtainable in tests of: 

fineness 75 

specific gravity 61 

tensile strength 150 

time of setting 99 

transverse strength 217, 234 

Acid, sulphuric, in cement 11 

(See also Calcium sulphate.) 

Acid, carbonic, in cement 11 

Adhesion tests 217 

Adulterations, tests for 204, 236 

Age, of cement. (See Seasoning.) 
Aggregate. (See Sand and Stone.) 

Air hardened mortars 133 

Alkalies, in cement 11 

Alumina, in cement 9 

Analysis, chemical 184 

equipment for 206 

methods of 185 

rapid methods for control work 201 
results of, on natural cement. 256 

on Portland cement 8 

on raw materials 17 

on slags and slag cements 267 

significance of 184 

Apparatus. (See Equipment.) 
Apparent density: 

tests of 51 

value of tests of 50 

Approximate tests for: 

fineness 226 

purity 2m 

soundness 234 

tensile strength 229 

time of setting 228 

transverse strength 232 

Bags: 

inspection of 36 

sealing 34 

weight of, of natural cement. 254 

of Portland cement 280 

Barrels: 

inspection of 36 

weight of, of natural cement... 254 

of Portland cement 280 

Bearing surfaces: 

for tensile tests 146 

for compression tests 213 

Boiling tests. (See Soundness.) 
Briquettes: 

effect of eccentricity in placing 147 

form of 114 

mechanical formers 12(5 

machines for testing 136 

methods of breaking 14.S 

methods of making 117 

moulds for ll"* 

storing 130 

Broken stone. (See Stone.) 
Burning: 

efl'ect on soundness 150 

effect on specific gravity 4(5 

effect on strength 103 

effect on time of setting S2 

natural cement 253 

Portland cement 25 



Page. 
Calcium sulphate: 

allowable proportions of 

11, 185. 2S2 

effect on soundness 1.56 

effect on strength 84. 103 

effect on time of setting 82 

methods of determining ..191, 195 
Calcination of cement. (See Burn- 
ing.) 
Calculation of mixtures of raw ma- 
terials for Portland ce- 
ment 18 

Carbonic acid. (See Acid, carbonic.) 

Cement rock 15 

analysis of 17, 185 

Classification of cements 1 

Clinker: 

burning of 25 

examination of 26, 206 

Clip: 

breaks in 146 

forms of 145 

standard form of 145 

Color of cement 10, 37, 258, 269 

Composition. (See Analysis.) 
Compressive strength: 

form of specimens for tests of 212 

machines for testing 214 

ratio to tensile strength 215 

tests of 212 

versus tensile strength for rou- 
tine 101 

Consistency: 

effect on soundness 162 

effect on tensile strength 108 

effect on time of setting 88 

methods of determining 03 

normal 02 

of sand mortars 110 

Constancy of volume. (See Sound- 
ness.) 

Constitution of cement 12 

Control analysis. (See Analysis.) 
Cost : 

of equipment for chemical an- 
alysis 2tH> 

for physical testing 242 

of testing 242 

Crushing strength. (See Compres- 
sion.) 
Cubes of conrroto. (Sec Compres- 
sion and Moulds.) 
Damp closets for cement briquettes. 

131. 2.30 

Deflnilions 1 

(See also material or test in question.) 
Density, a|)parpnt. (See Apparent 

density.) 
Density. (See Specific Crnvlfy.) 
ICccenlriclly. olYeit of, on tensile 

briquettes 147 

I'^nvlronment : 

effect of. on soundness 157 

on spocilU" gravity 47 

on tensile streiiKlJi 107 

on time of setting ""> 



3i8 



INDEX. 



Page. 
Equipment: 

for chemical analysis 207 

for complete physical testing. 239 

for field laboratories 240 

for making rough tests 237 

Expansion of cement 158 

measurement of 160 

Fineness, of cement: 

effect on soundness 157 

specific gravity 49 

strength 105 

time of setting 90 

weight 50 

importance of 63 

interpretation of results of 79 

mechanical appliances for test- 
ing 70 

methods of testing 64, 226 

sieves for testing 66 

specifications for 281, 283 

Fineness, of sand 223 

Force, requisite for testing cement. 241 
Formulas, for amount of mixing 

water in sand mortars 110 

Free lime, in cement. (See Lime.) 
Gaging (See also Consistency): 

effect of thorough 92, 108 

mechanical appliances for ... 126 

method of, by hand 117 

water for sand mortars 110 

with sea water 112 

Grinding cement, machinery for. 22, 254 

(See also Fineness.) 
Gypsum. (See Calcium sulphate.) 

History, of Portland cement 3 

Hot water tests. (See Soundness.) 
Humidity: 

effect of, on fineness 73 

on specific gravity 50 

on time of setting 90 

Improved cements: 

constitution of 263 

strength of 264 

tests of 264 

Inspection of cement 36 

Interpretation of: 

approximate tests 237 

chemical analyses 208 

specifications 284 

tests of fineness 79 

soundness 183 

specific gravity 61 

tensile strength 153 

time of setting 99 

Iron oxide, in cement 10 

Kilns: 

for burning natural cement . . 2.53 
rotary, for Portland cement.. 25 
stationary, for Portland cement 28 
Labor. (See Force.) 

Lime, in cement 9, 184 

effect of excess of, on soundness 156 

on strength 103 

free 103, 156 

Limestone: 

analysis of 17 

for cement manufacture 15 

method of analyzing 185 

Loam in sand 223 

Machines for: 

abrasion tests 219 

breaking briquettes 136 

compression tests 214 

making briquettes 127 

mixing mortar 126 

rough tests 230 

transverse tests 233 



Page. 
Machine mixing of mortar versus 

hand 128 

Machinery for cement manufacture 2^ 

Magnesia in cement 10 

allowable proportions of 10,185,282 
Manufacture: 

of natural cement 252 

of Portland cement 19 

raw materials for, of Portland 

cement 15 

of slag cement 268 

various processes of 19 

Marl, for cement manufacture ..15, 30 

analysis of 17 

Marking briquettes 135 

Microscopical tests 206 

Mills, for grinding cement 22, 253 

Mixed cements: 

tests of 274 

varieties of 272 

Mixing mortar for cement testing. 117 

Mixing samples 39 

Modulus of rupture in flexure.. 217, 233 
ratio to tensile strength. . .217, 234 
Moist closet. (See Damp closet.) 
Moisture. (See Humidity.) 
Moulding: 

by hand 120 

by machine 126 

hand versus machine 128 

methods of 117 

Moulds: 

cleaning 117 

for adhesion tests 218 

for compression tests 213 

for tensile tests 115 

for transverse tests 216, 232 

rough forms for approximate 

tests 231 

Mortar mixing. (See Mixing.) 
Natural cement: 

adaptability 263 

composition 255 

definition 1, 252 

distinguishing characteristics . 2 

manufacture 252 

specifications for 263, 282 

tests of 258 

weight of 258 

Normal pats. (See Soundness.) 
Numbering briquettes. (See Marking.) 

Oiling moulds 117 

Operation of laboratory 243 

cost of 242 

labor required for 241 

methods of 244 

Pat tests. (See Soundness.) 

Permeability, tests of 221 

Plaster of Paris. (See Calcium sul- 
phate.) 

Porosity, tests of 220 

Portland cement: 

composition 7 

definition 1 

manufacture 19 

raw materials for '. 15 

specifications for 280 

weight of 280 

Pozzuolana cement (See also Slag 
cement) : 

definition 2 

varieties of 264 

Production of cement. (See Statistics.) 
Purity, tests of. (See Adulteration.) 
Puzzolan cement. (See Pozzuolana.) 

Qualities desirable in cement 41 

Rate of applying stress in tensile 

tests 147 




INDEX. 



319 



Page. 
Ratio of tensile strength to com- 
pressive strength 214 

to shearing strength 219 

to transverse strength .217,, 234 
Raw materials for Portland cement:' 

composition of 17 

different varieties of 15 

proportioning 18 

Reception of cement shipments ... 34 

Records of tests 244 

Reports of tests 249 

Roman cement, definition 2 

Rosendale cement, definition 2 

Rotary kilns: 

for dry materials 25 

for wet materials 30 

versus stationary kilns 29 

Sampling, methods of 37 

Sand: 

comparative tests of 224 

effect of character of, on ten- 
sile strength 112, 223 

fineness of 223 

percentage of voids in 224 

purity of 223 

specific gravity of 224 

standard 112 

versus neat tests 102 

water for gaging 110 

Sand cement: 

cost of 272 

definition 2 

manufacture 272 

tests of 272 

Seals for cement bags 34 

Seasoning: 

effect of, on soundness 157 

on specific gravity 47 

on strength 104 

on time of setting 88 

necessity for 61, 104 

Setting, rate or time of: 

accuracy of test 99 

apparatus for testing 94 

approximate methods of testing 228 

definition 80 

effect of calcium sulphate 83 

composition 82 

consistency 88 

environment 90 

fineness 90 

gaging 92 

seasoning 88 

temperature 88, 91 

interpretation of results of . . 99 

methods of testing 90 

normal consistency for 92 

rise in temperature during 91 

specifications for 281, 283 

theory of ....^ 80 

Shearing, tests of 219 

ratio to tensile strength 2.19 

Shot machines for cement testing . . 139 
Sieves for cement: 

different sizes of 00 

Irregularities in OS 

size and shape of 74 

specifications for 70 

use of 70 

Sieves for sand testing 223 

Sieves for stone testing 224 

Silica, in cement 9 

Silica cement. (See Sand Cemev^L) 
Slag: 

detection of, In Portland ce- 
ment 204. 2!'; 

for manufacture of Portland 

comont 10, 32 

slag cement 2iW 



Page. 
Slag cement: 

adaptability 271 

composition ',,\\ 265 

definition '2 264 

distinguishing characteristics .' 269 

manufacture 268 

specifications for 271 

tests of 269 

weight of 269 

Soundness: 

accelerated tests 166 

apparatus for testing ..." 171 

effect of composition 153 

fineness 157 

seasoning 157 

interpretation of resuKs oC 

tests of 183 

methods of testing 1.58 

normal tests 162 

value of accelerated tests .!!! 175 
Specifications for: 

natural cement 282 

Portland cement 280 

discussion of 275 

interpretation of ." 284 

sieves for cement testing 70 

standard sand 112 

Specific gravity: 

accuracy of test 61 

apparatus for testing 52 

definition 43 

effect of adulteration 46 

composition 49 

degree of burning 46 

fineness 40 

humidity r^Q 

seasoning 47 

interpretation of results of 

tests of 61 

methods of testing 58 

sources of error in testing 57 

specifications for 61, 281, 283 

treatment of sample before 

testing 56 

Stationary kilns. (See Kilns.) 
Statistics of natural cement industry 2."»2 
of Portland cement industry.. 3 
of slag cement industry ...".., 205 
Stone, broken: 

comparative tests of 225 

size of 224 

specific gravity of 225 

voids in 225 

Storage of cement shipments 35 

Storage of samples 40 

Storage of briquettes: 

appliances for l.'U, i;U 

before ininuTsion 1.30 

during inunersion 1,33 

in air versus water 132 

Strength. (See Tensile. roni|)rcs- 

sivo. etc.) 
Sulphate of llnio. (See Calcium sul- 
phate.) 
Suli)hur: 

In Portland cement 11 

In sl!ig ctMiuMii 200 

allowable iiro|)ortlon of 2tMJ, 271 
Suli)1nni(' acid. (See Add. sulphuric.) 
Tanks for briquettes. (Sec Storage.) 
Tt'inpcralni*': 

of nilxliiK water, effect on 

shcnKlb 112 

efft'cf on time of settlnR .. .*<S 
of sloniRe water. ofTeot on 

strenKth 133 



320 



INDEX. 



Page. 



Temperature: 

of testing room, effect on spe- 
cific gravity 57 

effect on strength 107 

effect on time of setting... 90 

rise in. during setting 91 

Tensile strength: 

accuracy of test 150 

appliances for storing briquettes 134 
briquettes breaking in clips... 146 

definition 101 

effect of amount of gaging l-!0 

amount of mixing water.. 108 

character of sand 112 

composition 102 

environment during hard- 
ening 133 

during setting 130 

of sample 107 

fineness 105 

form of clips 145 

purity of mixing water 112 

rate of stress in breaking. 147 

seasoning 104 

temperature of mixing 

water 112 

treatment during test 147 

form of briquette 114 

hand versus machine made 

briquettes 128 

interpretation of results of 

tests of 158 

marking briquettes 135 

mechanical devices for mixing 126 

for moulding 127 

methods of mixing 117 

of moulding 122 

moulds for briquettes 115 

neat versus sand tests 102 

number of briquettes to test . . 148 

periods for testing 102 

ratio to compressive strength 214 

to shearing strength 219 

to transverse strength .217, 234 
for employment in 
routine 101 



Page. 

Tensile strength: 

retrogression in 103, 152 

specifications for 154, 281, 283 

testing machines 136, 230 

accuracy of various types. 

145, 230 
adaptability of various types 136 
characteristics of various 

types 136 

form of clip 145 

operation of 139 

requisites for 1.36 

simple forms of 230 

theory of growth in 103, 152 

Testing machines. (See Compres- 
sive, Tensile, etc.) 
Tests. (See particular test in ques- 
tion.) 
Time of setting. (See Setting.) 
Transverse strength: 

accuracy of test 217, 234 

apparatus for testing 217 

methods of testing 217 

moulds for specimens 216, 231 

ratio to tensile strength. .217, 234 

rough method of testing 232 

Underburning: 

effect of, on soundness 156 

on specific gravity 46 

on strength 9, 102 

on time of setting 9, 80 

Unsoundness. (See Soundness.) 
Voids: 

determination of, in sand 224 

in stone 225 

Volume constancy. (See Soundness.) 
Water. (See Consistency, Setting, 

and Tensile Strength.) 
Weight (See also Apparent Density) : 

of natural cement 258 

of Portland cement 37, 280 

Wire cloth for cement sieves 67 

examination of 68 

specifications for 70 

Yield tests of cement and mortar.. 222 



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